Battle of Sio
Encyclopedia
The Battle of Sio, fought between December 1943 and March 1944, was the breakout
and pursuit
phase of General
Douglas MacArthur
's Huon Peninsula campaign
, part of the New Guinea campaign
of World War II.
Following the defeat of the Japanese
in the Battle of Sattelberg
, Australian Army
forces broke through the Japanese positions around Finschhafen
. Constant pressure from U.S. Navy PT boats, Australian land forces and Allied aircraft brought the Japanese logistical system to the brink of collapse, resulting in disease, malnutrition and privation for the Japanese soldiers. Meanwhile the Allied supply system grappled with the problems of terrain and climate, particularly inclement weather and rough monsoonal seas that hampered and occasionally prevented delivery of supplies by sea.
Australian and Papuan troops advanced along the coast of the Huon Peninsula
, employing infantry, tanks, and air strikes against the Japanese positions, which were generally sited at creek crossings in the jungle. The advancing infantry kept strictly within range of the supporting artillery, which was liberally employed in the early stages of the operation. Using tactics that exploited the firepower of Australian artillery and armour, the Australian and Papuan troops inflicted heavy and disproportionate casualties on the Japanese as they advanced, ultimately linking up with the American forces at Saidor
. Hundreds of Japanese soldiers were killed; thousands more died from disease, malnutrition, exhaustion and suicide. However, the Allies failed to seize the opportunity to completely destroy the Japanese forces.
During the advance, Australian troops captured Japanese cryptographic materials. This would have an important effect on the subsequent course of the war against Japan in the South West Pacific, as it permitted codebreakers in Australia and the United States to read Japanese Army messages on a much greater scale than had been previously possible.
began with spectacular victories in the landing at Lae
and the landing at Nadzab
but then faltered in the face of inclement weather, unfavourable terrain, and—above all—tenacious and aggressive Japanese opposition on land and in the air. The initiative passed to Hatazō Adachi
's Japanese Eighteenth Army which launched a series of counter-attacks against Major General
George Wootten
's 9th Division in the Battle of Finschhafen
. At the Battle of Sattelberg
, Wootten finally inflicted a crushing defeat on Adachi.
The Japanese were defeated, but they did not leave the area. Lieutenant General
Shigeru Katagiri
, the commander of the Japanese 20th Division
, ordered the 80th Infantry Regiment
to hold the Wareo area to protect the withdrawal of the 79th Infantry Regiment
and other units. The 2nd Battalion, 238th Infantry Regiment
was to act as a rearguard on the coast. Lieutenant General
Frank Berryman, the commander of Australian II Corps, now urged Wootten to commence a coastal advance that would cut the Japanese supply lines and force Adachi to retreat from the Huon Peninsula
if he were not already doing so. Wootten took a more cautious approach. The Battle of Wareo proved that the Japanese intended to defend the area. After a fierce fight, Wootten managed to drive the Japanese from the high ground around Sattelberg and Gusika. In early December, Adachi finally ordered all his troops to withdraw to Sio
. Wareo was captured by the Australians on 8 December and the last Japanese rearguards left the area on 15 December. Meanwhile, Berryman's coastal advance had commenced on 5 December.
line, and therefore took time to realise that the Japanese force could not be maintained over an inland track, as was first assumed. Operations soon confirmed that the Japanese were dependent on a coastal supply line. During the Battle of Sattelberg
, the Allies set out to cut this supply line. A three-pronged approach was taken:
By December, the pitiful condition of Japanese prisoners confirmed for the Australians that "the Japanese logistic system was in the final stages of breakdown". Between 9 and 13 December, PT boats sank 23 barges, most of them south of Sio. On 7 January, the PT boats also attacked a submarine. No less than twelve barges were destroyed on the night of 8 January, one of which was loaded with ammunition and another with around 70 troops. On 9 January, PT boats attacked a group of six barges, which attempted to fight back. One barge was seen to sink. Another patrol engaged eight barges and destroyed two. A third patrol found six barges on a beach and destroyed them. Then on 10 January, three PT boats sank three troop-carrying barges, taking one Japanese prisoner. The same night, two barges were also sunk north of Sio Island. When General Berryman saw Vice Admiral
Thomas C. Kinkaid
on 14 December, he made a point of congratulating him on the work his PT boats were doing.
Lieutenant General Tsutomu Yoshihara, Chief of Staff of the Japanese Eighteenth Army recalled:
The main Australian advance was by infantry
-tank
-engineer
teams moving along the coastal tracks. Japanese positions were generally sited at creek crossings in the jungle
. The advancing infantry kept strictly within range of the supporting artillery, except for short periods during the latter stages of the operation when Japanese opposition was negligible and the difficulty of moving the artillery forward quickly was too great. A secondary outflanking movement would be made inland, over the higher ground, which was usually coral
cliffs covered by Kunai grass and rising as high as 4000 feet (1,219.2 m). Since the Japanese intent was to delay rather than fight to the death, a threat to their escape route would usually prompt a withdrawal. When this did not occur, the position was reduced by a combination of manoeuvre and tank, mortar, and artillery fire. During the early part of the advance, some 4,700 rounds were fired in just one day; but during the entire 5th Division advance from Sio to Saidor, only 30 rounds were fired. The advance was made in a series of bounds, the objective of which was usually to secure sheltered beachheads.
Allied supply was entirely by sea. Amphibian scouts from the US 532nd Engineer Boat and Shore Regiment (EBSR) of the US 2nd Engineer Special Brigade
, wearing Australian uniforms, advanced with the infantry and reconnoitred beaches from the landward side as they were secured. If a beach looked suitable, a second reconnaissance was made from the sea. Once a beach was selected, a shore party was brought in by landing craft to set up an administrative area. Engineers improved the coastal track to enable supplies to units moving along it to be brought up by jeep
s but supplies for units moving inland over the high ground had to be brought by native carriers. Artillery guns were brought forward over the tracks, or else were moved by Landing Craft Mechanised (LCMs) of the 532nd EBSR. Tanks normally moved along the tracks but used LCMs to bypass obstacles. As the advance continued, new beachheads were opened up while rearward ones were closed. The advance was halted on occasion to allow for the guns to be brought forward or sufficient supplies to be accumulated at the forward beachhead.
The major problem was the weather. The monsoon
caused rough seas that precluded the use of the small Landing Craft, Vehicle, Personnel (LCVPs) and restricted the operations of the larger LCMs. Because of the extremely rough seas—the most difficult that the 532nd EBSR had ever encountered—most supply missions were by night when tidal conditions were most favourable. Wootten insisted that at least seven days' supplies be available in forward areas in case the weather prevented the LCMs from running. II Corps made available two trawlers, manned by the 1st Water Transport Group, to deliver rations. The Australian Army also moved supplies by DUKW
s.
Wootten designated Brigadier
C. R. V. Edgar's 4th Infantry Brigade, a Militia
formation, for the initial phase of the coastal advance, reserving his veteran Australian Imperial Force
brigades for the Battle of Wareo. The brigade consisted of the 22nd and 29th/46th
Infantry Battalions from Victoria
and the 37th/52nd Infantry Battalion
from Tasmania
. Each battalion was allotted a team of advisors from the 9th Division. Under Edgar's command was C Squadron, 1st Tank Battalion, with seven Matilda tank
s, 9 Platoon, C Company, Papuan Infantry Battalion
, and detachments from the 532nd EBSR, Australian New Guinea Administrative Unit
(ANGAU), Australian Army Service Corps
(AASC) and Australian Army Medical Corps
(AAMC). In support were the sappers of the 2/7th Field Company and the 24 25-pounders of the 2/6th Field Regiment. In case Edgar got into trouble, the 20th Infantry Brigade
was in reserve, on six hours notice.
To support the advance, a beach maintenance area was prepared at a beach at the mouth of the Kalueng River, which involved removing underwater and landward obstacles. So that the tanks and jeeps could immediately support the advance, a bridge was required over the Kalueng River. A preliminary operation by the 22nd Infantry Battalion on 3 December 1943 secured a crossing area and a log bridge was constructed. The operation jumped off on 5 December, with the 29th/46th Infantry Battalion passing through the bridgehead established by the 22nd. It soon came under sporadic enemy fire, and a tank was disabled by a land mine. In the face of mounting opposition, the advance was halted near the lagoon. It resumed the next day, and the Japanese withdrew after an artillery bombardment, their orders being "while avoiding any decisive engagement" to "carry out successful resistance to try to delay the enemy advance". This became the pattern, with the Japanese preferring to withdraw rather than suffer heavy casualties. On 10 December, Edgar brought all three of his battalions into the line and by 14 December they were closing in Lakona, a key position on the 20th Division's retreat route.
The tanks had difficulty keeping up with the advance. One obstacle was mines. On the first day, the 2/7th Field Company lifted fourteen mines but a tractor broke a track running over a mine. On 7 December, two more tanks were damaged by mines, one beyond repair. The sappers then cut a new track which they corduroyed
. To support the attack on Lakona, the tanks had to cross a creek with steep coral banks, swollen by a torrential downpour. While efforts were made to bring up a compressor, tanks fired into banks and holes were packed with explosives and detonated. On the evening of 16 December, the infantry were joined by five Matilda tanks, and the Japanese positions were overrun. Some 47 Japanese dead were counted; another 17 were killed in mopping-up operations the next day. On 20 December, aided by four Matilda tanks and 750 rounds from the 25-pounders, the 4th Infantry Brigade occupied the Fortification Point area. Between 5 and 20 December the 4th Infantry Brigade reported 65 killed and 136 wounded. Japanese casualties were 420 killed and 136 found dead, victims of disease, malnutrition and suicide. Only six Japanese prisoners were taken.
, Berryman and Wootten visited the acting brigade commander, Lieutenant Colonel
N. W. Simpson, and emphasised that the brigade was to minimise casualties where possible by employing artillery and tanks. That afternoon, the lead company of the 2/13th Infantry Battalion reached Hubika. The battalion diarist recorded:
A halt was called for Christmas while supplies were brought up. Units had a rest day. Most dined on turkey, ham, roast potatoes and Christmas pudding
, and Christmas services were held. General Blamey insisted that Christmas fare be available to all units, and extraordinary efforts were made to carry out his directive. In one instance, a Piper Cub
of No. 4 Squadron RAAF
dropped Christmas fare to a Papuan Company on a long range patrol. The advance resumed on 27 December, preceded by air strikes by 18 B-25 Mitchell
and 12 Boston bombers. The 2/15th Infantry Battalion and tanks of A Squadron, 1st Tank Battalion took the lead on 31 December; they reached Sialum on 2 January 1944. This had a sheltered beach which served a maintenance area. That day, the American landing at Saidor
placed a large force across the Japanese escape route.
Before moving over the mountains, the 20th Division headquarters elected to destroy its cryptographic materials rather than carry them. As the wet weather made burning them page by page a slow and difficult process, and a fire might attract the attention of the Allied Air Forces, someone decided to simply bury them in a steel trunk in a stream bed. An Australian sapper
checking the stream bed for booby traps with a metal detector
discovered it, and it was dug up in the belief that it was a mine. An intelligence officer recognised the contents as code books and soon it was on its way to the Central Bureau
in Brisbane
. There, the pages were carefully dried out and photographed. On 4 February 1944, Central Bureau codebreakers decrypted a thirteen-part message that laid out the decisions reached at a conference of high ranking Japanese officers. Copies of the material were quickly sent to Arlington Hall
. In January 1944, Arlington Hall had decrypted 1,846 Japanese army messages. In March 1944, with the Sio code books in hand, it decrypted 36,000 messages.
On 11 January a platoon of the 2/17th Infantry Battalion
replaced a rope ladder, and after climbing it and two wooden ladders reached an area atop a cliff which had once been a Japanese headquarters. It would have been a formidable position if defended, but it was not. The main body of the battalion followed the next day. The Goaling River was crossed in small boats left behind by the Japanese on 13 January and it entered Nambariwa, where one prisoner was taken, six Japanese were shot, and nine found dead. On 15 January, Sio was taken. The Sio-Nambariwa area was found to have been the principal Japanese supply area, and a large number of fuel, supply, and stores dumps were found. During the advance from Fortification Point to Sio, 303 Japanese had been killed or found dead, and 22 captured. The 20th Infantry Brigade had lost 3 killed and 13 wounded, but 958 had been evacuated sick, mostly with malaria
, but an epidemic of dengue had also taken its toll. Large quantities of Japanese equipment had been captured, including six 75 mm guns
, three 37 mm guns
and three 20 mm guns
.
At 1800 on 20 January 1944, the headquarters of the Major General A. H. Ramsay's 5th Division, which had come up from Lae
, replaced that of the 9th Division. At the same time the 8th Infantry Brigade
replaced the 20th. This formation, which had spent much of the war on garrison duty in Western Australia, had begun departing Cairns on 10 January. The original intention had been for this brigade to go to Lae to relieve the 29th Infantry Brigade, which had fought in the Salamaua-Lae campaign
, but in December it was decided to ship the 8th Infantry Brigade direct to Finschhafen. The brigade contained three infantry battalions, the 4th, 30th
and 35th
, all from New South Wales
. It also still had the support of the 2/12th Field Regiment, 532nd EBSR, and A Company, Papuan Infantry Battalion. The brigade suffered its first casualties on the night of 21/22 January in a friendly fire
incident, which was a common occurrence with units inexperienced in jungle warfare
. Two Australians were killed and two wounded by their own comrades.
On 22 January a native reported seeing seven Japanese in the hills south west of Sio and a patrol was sent out under Corporal
Bengari to investigate. On arriving in the vicinity on 24 January, a local reported that another 22 Japanese had arrived. The next morning, Bengari and his five companions ambushed the Japanese and killed them all before they could fire a shot. Wirraway
and Boomerang
aircraft of No. 4 Squadron RAAF scouted ahead of the advance. Its aerial reconnaissance work let the Australians and Papuans know where opposition could be expected, thereby speeding up the advance. The pilots noted Japanese parachutes, signs that the Japanese were receiving supplies by air. On 4 February, the Australians were also forced onto air supply, as swollen rivers washed out a number of bridges.
Each day the Papuans killed 12 to 15 Japanese, but not until 8 February was the Japanese rearguard encountered at Weber Point and a formal attack made. Five Japanese were killed. In all, 53 Japanese were killed and four captured that day. Two Australians were wounded. The next day another 61 Japanese were killed and 9 captured, this time without any Australian casualties. On 10 February, the 30th Infantry Battalion encountered two American soldiers at Yagomai, thereby linking up with the American force at Saidor.
The 8th Infantry Brigade now began to mop up the area. On 18 February, the 35th Infantry Battalion attacked a Japanese force near Gabutamon, killing 40. Finding a force of about 100 Japanese at nearby Tapen, they attacked, killing another 52 Japanese for the loss of one man wounded, while the Papuans on their flanks killed another 51, of whom 43 were accounted for by Corporal Bengali and two other Papuans. The next day, the Papuans found and killed another 39 Japanese in the vicinity. At Tapen, the Australians and Papuans also found evidence that the Japanese had resorted to cannibalism
. In the period 20 January – 1 March 1944, 734 Japanese were killed, 1,775 found dead and 48 were captured. Australian casualties came to four killed and six wounded.
that had originally been forward of Sio survived the withdrawal, and many of them were rendered ineffective through wounds, sickness, malnutrition and exhaustion. However, the opportunity to destroy the Japanese 51st Division
was not seized. These troops would live to fight the Americans at the Battle of Driniumor River
later in the year, and the Australians in the Aitape–Wewak campaign in 1945. On the other hand, the new base at Finschhafen was no longer threatened by the Japanese, and would became an important staging point for the Western New Guinea campaign
. The capture of the Japanese ciphers at Sio would allow General MacArthur to carry out Operations Reckless and Persecution
with a plan based upon sound intelligence rather than just his own intuition.
Breakout (military)
A breakout is a military operation to end a situation of encirclement or siege. It is used in contexts such as: "The British breakout attempt from Normandy"....
and pursuit
Breakthrough (military)
A breakthrough occurs when an offensive force has broken the enemy defensive line, and is rapidly exploiting the gap.Usually, large force is employed on a relatively small portion of the front to achieve this...
phase of General
General (United States)
In the United States Army, United States Air Force, and United States Marine Corps, general is a four-star general officer rank, with the pay grade of O-10. General ranks above lieutenant general and below General of the Army or General of the Air Force; the Marine Corps does not have an...
Douglas MacArthur
Douglas MacArthur
General of the Army Douglas MacArthur was an American general and field marshal of the Philippine Army. He was a Chief of Staff of the United States Army during the 1930s and played a prominent role in the Pacific theater during World War II. He received the Medal of Honor for his service in the...
's Huon Peninsula campaign
Huon Peninsula campaign
The Huon Peninsula campaign was a series of battles in the New Guinea campaign of the Second World War. Australian forces assaulted Japanese bases on the Huon Peninsula....
, part of the New Guinea campaign
New Guinea campaign
The New Guinea campaign was one of the major military campaigns of World War II.Before the war, the island of New Guinea was split between:...
of World War II.
Following the defeat of the Japanese
Imperial Japanese Army
-Foundation:During the Meiji Restoration, the military forces loyal to the Emperor were samurai drawn primarily from the loyalist feudal domains of Satsuma and Chōshū...
in the Battle of Sattelberg
Battle of Sattelberg
The Battle of Sattelberg took place during the Huon Peninsula campaign of the Second World War. Involving forces from Australia, the United States and Japan, the fighting centred around the Sattelberg mission station which was situated atop a hill about above sea level, approximately inland from...
, Australian Army
Australian Army
The Australian Army is Australia's military land force. It is part of the Australian Defence Force along with the Royal Australian Navy and the Royal Australian Air Force. While the Chief of Defence commands the Australian Defence Force , the Army is commanded by the Chief of Army...
forces broke through the Japanese positions around Finschhafen
Finschhafen
Finschhafen is a district on the northeast coast of the Morobe province of Papua New Guinea. It is named after the port of the same name.The port was discovered in 1884 by the German researcher Otto Finsch. In 1885 the German colony of German New Guinea created a town on the site and named it...
. Constant pressure from U.S. Navy PT boats, Australian land forces and Allied aircraft brought the Japanese logistical system to the brink of collapse, resulting in disease, malnutrition and privation for the Japanese soldiers. Meanwhile the Allied supply system grappled with the problems of terrain and climate, particularly inclement weather and rough monsoonal seas that hampered and occasionally prevented delivery of supplies by sea.
Australian and Papuan troops advanced along the coast of the Huon Peninsula
Huon Peninsula
Huon Peninsula is a large rugged peninsula on the island of New Guinea in Morobe Province, eastern Papua New Guinea. It is named after French explorer Jean-Michel Huon de Kermadec who discovered it along with his personal assistant and porter, Henry Ole. The peninsula is dominated by the steep...
, employing infantry, tanks, and air strikes against the Japanese positions, which were generally sited at creek crossings in the jungle. The advancing infantry kept strictly within range of the supporting artillery, which was liberally employed in the early stages of the operation. Using tactics that exploited the firepower of Australian artillery and armour, the Australian and Papuan troops inflicted heavy and disproportionate casualties on the Japanese as they advanced, ultimately linking up with the American forces at Saidor
Landing at Saidor
The Landing at Saidor was an Allied amphibious landing at Saidor, Papua New Guinea on 2 January 1944 as part of Operation Dexterity during World War II. In Allied hands, Saidor was a stepping stone towards Madang, the ultimate objective of General Douglas MacArthur's Huon Peninsula campaign...
. Hundreds of Japanese soldiers were killed; thousands more died from disease, malnutrition, exhaustion and suicide. However, the Allies failed to seize the opportunity to completely destroy the Japanese forces.
During the advance, Australian troops captured Japanese cryptographic materials. This would have an important effect on the subsequent course of the war against Japan in the South West Pacific, as it permitted codebreakers in Australia and the United States to read Japanese Army messages on a much greater scale than had been previously possible.
Background
General Douglas MacArthur's Operation CartwheelOperation Cartwheel
Operation Cartwheel was a major military strategy for the Allies in the Pacific theater of World War II. Cartwheel was a twin-axis of advance operation, aimed at militarily neutralizing the major Japanese base at Rabaul...
began with spectacular victories in the landing at Lae
Landing at Lae
The Landing at Lae was an amphibous landing, as part of ', to the east of Lae in the Salamaua-Lae campaign of World War II between 4–6 September 1943....
and the landing at Nadzab
Landing at Nadzab
The Landing at Nadzab was an airborne landing on 5 September 1943 during the New Guinea campaign of World War II that began with a parachute drop at Nadzab in conjunction with the Landing at Lae....
but then faltered in the face of inclement weather, unfavourable terrain, and—above all—tenacious and aggressive Japanese opposition on land and in the air. The initiative passed to Hatazō Adachi
Hatazo Adachi
was a general in the Imperial Japanese Army during World War II.-Early career:Adachi was born into an impoverished samurai family in Ishikawa Prefecture in 1890...
's Japanese Eighteenth Army which launched a series of counter-attacks against Major General
Major General (Australia)
Major General is a senior rank of the Australian Army, and was created as a direct equivalent of the British military rank of Major General. It is the third-highest active rank of the Australian Army, and is considered to be equivalent to a two-star rank...
George Wootten
George Wootten
Major General Sir George Frederick Wootten KBE, CB, DSO & Bar, ED , was an Australian soldier, public servant, right wing political activist and solicitor. He rose to the rank of temporary Major General during World War II....
's 9th Division in the Battle of Finschhafen
Battle of Finschhafen
The Battle of Finschhafen was part of the Huon Peninsula campaign during the Second World War between September and October 1943 between Australian and Japanese forces...
. At the Battle of Sattelberg
Battle of Sattelberg
The Battle of Sattelberg took place during the Huon Peninsula campaign of the Second World War. Involving forces from Australia, the United States and Japan, the fighting centred around the Sattelberg mission station which was situated atop a hill about above sea level, approximately inland from...
, Wootten finally inflicted a crushing defeat on Adachi.
The Japanese were defeated, but they did not leave the area. Lieutenant General
Lieutenant General
Lieutenant General is a military rank used in many countries. The rank traces its origins to the Middle Ages where the title of Lieutenant General was held by the second in command on the battlefield, who was normally subordinate to a Captain General....
Shigeru Katagiri
Shigeru Katagiri
Lieutenant General Shigeru Katagiri was a senior officer in the Imperial Japanese Army during World War II.He was the commanding officer of 27th Cavalry Regiment in 1936, before being attached as the Chief of Staff 1st Division between 1937 until 1939. He was then attached to the Army Cavalry...
, the commander of the Japanese 20th Division
20th Division (Imperial Japanese Army)
was an infantry division in the Imperial Japanese Army. Its call sign was the .-History:The 20th Division and the 19th Division were raised on 24 December 1915 as a garrison force for Korea. After Japan's victory in the Russo-Japanese War, and subsequent occupation, and then annexation of Korea,...
, ordered the 80th Infantry Regiment
80th Infantry Regiment (Imperial Japanese Army)
The 80th Infantry Regiment was an infantry regiment in the Imperial Japanese Army. The regiment was attached to the 40th Infantry Brigade of the 20th Division. The regiment participated during the Second Sino-Japanese War and during the later stages of World War II, the regiment was in New Guinea,...
to hold the Wareo area to protect the withdrawal of the 79th Infantry Regiment
79th Infantry Regiment (Imperial Japanese Army)
The 79th Infantry Regiment was an infantry regiment in the Imperial Japanese Army. The regiment was attached to the 40th Infantry Brigade of the 20th Division. The regiment participated during the Second Sino-Japanese War and during the later stages of World War II, the regiment was in New Guinea,...
and other units. The 2nd Battalion, 238th Infantry Regiment
238th Infantry Regiment (Imperial Japanese Army)
The 238th Infantry Regiment was an infantry regiment in the Imperial Japanese Army. The regiment was attached to the 41st Division. The regiment participated during the Second Sino-Japanese War and during the later stages of World War II, the regiment was in New Guinea, as part of the Japanese...
was to act as a rearguard on the coast. Lieutenant General
Lieutenant General (Australia)
Lieutenant general is the second-highest active rank of the Australian Army and was created as a direct equivalent of the British military rank of lieutenant general. It is also considered a three-star rank....
Frank Berryman, the commander of Australian II Corps, now urged Wootten to commence a coastal advance that would cut the Japanese supply lines and force Adachi to retreat from the Huon Peninsula
Huon Peninsula
Huon Peninsula is a large rugged peninsula on the island of New Guinea in Morobe Province, eastern Papua New Guinea. It is named after French explorer Jean-Michel Huon de Kermadec who discovered it along with his personal assistant and porter, Henry Ole. The peninsula is dominated by the steep...
if he were not already doing so. Wootten took a more cautious approach. The Battle of Wareo proved that the Japanese intended to defend the area. After a fierce fight, Wootten managed to drive the Japanese from the high ground around Sattelberg and Gusika. In early December, Adachi finally ordered all his troops to withdraw to Sio
Sio, Papua New Guinea
-History:A Lutheran mission station was established at Sio in 1910.The town was occupied by Imperial Japanese forces during World War II and was a major operating base...
. Wareo was captured by the Australians on 8 December and the last Japanese rearguards left the area on 15 December. Meanwhile, Berryman's coastal advance had commenced on 5 December.
Offensive against the Japanese supply system
Early in October 1943, a special staff was established at II Corps Headquarters to study the Japanese supply system. It did not include an officer with experience in maintaining a large force over a native carrierPorter (carrier)
A porter, also called a bearer, is a person who shifts objects for others.-Historical meaning:Human adaptability and flexibility early led to the use of humans for shifting gear...
line, and therefore took time to realise that the Japanese force could not be maintained over an inland track, as was first assumed. Operations soon confirmed that the Japanese were dependent on a coastal supply line. During the Battle of Sattelberg
Battle of Sattelberg
The Battle of Sattelberg took place during the Huon Peninsula campaign of the Second World War. Involving forces from Australia, the United States and Japan, the fighting centred around the Sattelberg mission station which was situated atop a hill about above sea level, approximately inland from...
, the Allies set out to cut this supply line. A three-pronged approach was taken:
- Collecting centres for native foodstuffs and tracks leading from the coast were bombed by the US Fifth Air ForceFifth Air ForceThe Fifth Air Force is a numbered air force of the United States Air Force Pacific Air Forces . It is headquartered at Yokota Air Base, Japan....
. This not only reduced food stocks available to the Japanese, but also drove away the native carriers that the Japanese depended on to carry their supplies up from the coast. - PT boatPT boatPT Boats were a variety of motor torpedo boat , a small, fast vessel used by the United States Navy in World War II to attack larger surface ships. The PT boat squadrons were nicknamed "the mosquito fleet". The Japanese called them "Devil Boats".The original pre–World War I torpedo boats were...
s of Task Group 70.1 attempted to interdict barge traffic along the coast by night, while Fifth Air Force fighters conducted sweeps for barges by day. - The land forces attempted to physically cut the Japanese supply lines. The 9th Division captured Pabu, thereby cutting the most convenient inland track, while the landing at Long Island occupied an important barge staging area.
By December, the pitiful condition of Japanese prisoners confirmed for the Australians that "the Japanese logistic system was in the final stages of breakdown". Between 9 and 13 December, PT boats sank 23 barges, most of them south of Sio. On 7 January, the PT boats also attacked a submarine. No less than twelve barges were destroyed on the night of 8 January, one of which was loaded with ammunition and another with around 70 troops. On 9 January, PT boats attacked a group of six barges, which attempted to fight back. One barge was seen to sink. Another patrol engaged eight barges and destroyed two. A third patrol found six barges on a beach and destroyed them. Then on 10 January, three PT boats sank three troop-carrying barges, taking one Japanese prisoner. The same night, two barges were also sunk north of Sio Island. When General Berryman saw Vice Admiral
Vice admiral (United States)
In the United States Navy, the United States Coast Guard, the United States Public Health Service Commissioned Corps, the National Oceanic and Atmospheric Administration Commissioned Corps, and the United States Maritime Service, vice admiral is a three-star flag officer, with the pay grade of...
Thomas C. Kinkaid
Thomas C. Kinkaid
Thomas Cassin Kinkaid was an admiral in the United States Navy during World War II. He built a reputation as a "fighting admiral" in the aircraft carrier battles of 1942 and commanded the Allied forces in the Aleutian Islands Campaign...
on 14 December, he made a point of congratulating him on the work his PT boats were doing.
Lieutenant General Tsutomu Yoshihara, Chief of Staff of the Japanese Eighteenth Army recalled:
Tactics and logistics
Infantry
Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...
-tank
Tank
A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...
-engineer
Military engineer
In military science, engineering refers to the practice of designing, building, maintaining and dismantling military works, including offensive, defensive and logistical structures, to shape the physical operating environment in war...
teams moving along the coastal tracks. Japanese positions were generally sited at creek crossings in the jungle
Jungle
A Jungle is an area of land in the tropics overgrown with dense vegetation.The word jungle originates from the Sanskrit word jangala which referred to uncultivated land. Although the Sanskrit word refers to "dry land", it has been suggested that an Anglo-Indian interpretation led to its...
. The advancing infantry kept strictly within range of the supporting artillery, except for short periods during the latter stages of the operation when Japanese opposition was negligible and the difficulty of moving the artillery forward quickly was too great. A secondary outflanking movement would be made inland, over the higher ground, which was usually coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
cliffs covered by Kunai grass and rising as high as 4000 feet (1,219.2 m). Since the Japanese intent was to delay rather than fight to the death, a threat to their escape route would usually prompt a withdrawal. When this did not occur, the position was reduced by a combination of manoeuvre and tank, mortar, and artillery fire. During the early part of the advance, some 4,700 rounds were fired in just one day; but during the entire 5th Division advance from Sio to Saidor, only 30 rounds were fired. The advance was made in a series of bounds, the objective of which was usually to secure sheltered beachheads.
Engineer Special Brigade (United States)
Engineer Special Brigades were amphibious forces of the United States Army developed during World War II. Initially designated Engineer Amphibian Brigades, the first four brigades were redesignated ESBs in 1943.- Concept and Development :...
, wearing Australian uniforms, advanced with the infantry and reconnoitred beaches from the landward side as they were secured. If a beach looked suitable, a second reconnaissance was made from the sea. Once a beach was selected, a shore party was brought in by landing craft to set up an administrative area. Engineers improved the coastal track to enable supplies to units moving along it to be brought up by jeep
Jeep
Jeep is an automobile marque of Chrysler . The first Willys Jeeps were produced in 1941 with the first civilian models in 1945, making it the oldest off-road vehicle and sport utility vehicle brand. It inspired a number of other light utility vehicles, such as the Land Rover which is the second...
s but supplies for units moving inland over the high ground had to be brought by native carriers. Artillery guns were brought forward over the tracks, or else were moved by Landing Craft Mechanised (LCMs) of the 532nd EBSR. Tanks normally moved along the tracks but used LCMs to bypass obstacles. As the advance continued, new beachheads were opened up while rearward ones were closed. The advance was halted on occasion to allow for the guns to be brought forward or sufficient supplies to be accumulated at the forward beachhead.
The major problem was the weather. The monsoon
Monsoon
Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
caused rough seas that precluded the use of the small Landing Craft, Vehicle, Personnel (LCVPs) and restricted the operations of the larger LCMs. Because of the extremely rough seas—the most difficult that the 532nd EBSR had ever encountered—most supply missions were by night when tidal conditions were most favourable. Wootten insisted that at least seven days' supplies be available in forward areas in case the weather prevented the LCMs from running. II Corps made available two trawlers, manned by the 1st Water Transport Group, to deliver rations. The Australian Army also moved supplies by DUKW
DUKW
The DUKW is a six-wheel-drive amphibious truck that was designed by a partnership under military auspices of Sparkman & Stephens and General Motors Corporation during World War II for transporting goods and troops over land and water and for use approaching and crossing beaches in amphibious...
s.
Fortification Point
Brigadier
Brigadier is a senior military rank, the meaning of which is somewhat different in different military services. The brigadier rank is generally superior to the rank of colonel, and subordinate to major general....
C. R. V. Edgar's 4th Infantry Brigade, a Militia
Australian Army Reserve
The Australian Army Reserve is a collective name given to the reserve units of the Australian Army. Since the Federation of Australia in 1901, the reserve military force has been known by many names, including the Citizens Forces, the Citizen Military Forces, the Militia and, unofficially, the...
formation, for the initial phase of the coastal advance, reserving his veteran Australian Imperial Force
Australian Imperial Force
The Australian Imperial Force was the name given to all-volunteer Australian Army forces dispatched to fight overseas during World War I and World War II.* First Australian Imperial Force * Second Australian Imperial Force...
brigades for the Battle of Wareo. The brigade consisted of the 22nd and 29th/46th
29th/46th Battalion (Australia)
The 29th/46th Battalion was an infantry battalion of the Australian Army. It was formed in August 1942 by the amalgamation of two previously existing Militia battalions, the 29th and 46th, which were merged following a decision by the Australian government to release manpower from the military back...
Infantry Battalions from Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
and the 37th/52nd Infantry Battalion
37th/52nd Battalion (Australia)
The 37th/52nd Battalion was an infantry battalion of the Australian Army. Formed in 1930 from two previously existing Militia battalions, the battalion remained on the Australian order of battle until 1937. During World War II it was revived in 1942 and subsequently saw active service with the 4th...
from Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
. Each battalion was allotted a team of advisors from the 9th Division. Under Edgar's command was C Squadron, 1st Tank Battalion, with seven Matilda tank
Matilda tank
The Infantry Tank Mark II known as the Matilda II was a British infantry tank of the Second World War. It was also identified from its General Staff Specification A12....
s, 9 Platoon, C Company, Papuan Infantry Battalion
Royal Pacific Islands Regiment
The Royal Pacific Islands Regiment is an infantry regiment of the Papua New Guinea Defence Force . The regiment is descended from the Australian Army infantry battalions formed from native soldiers and Australian officers and non-commissioned officers in the territories of Papua and New Guinea...
, and detachments from the 532nd EBSR, Australian New Guinea Administrative Unit
Australian New Guinea Administrative Unit
The Australian New Guinea Administrative Unit was a civil administration of Territory of Papua and the Mandated Territory of New Guinea formed on 21 March 1942 during World War II...
(ANGAU), Australian Army Service Corps
Royal Australian Army Service Corps
The Royal Australian Army Service Corps was an Australian army unit. Formed shortly after the Federation of Australia on 1 January 1901, it was known as the Australian Army Service Corps . The MSC/AASC/RAASC served in World War I, World War II, as part of the British Commonwealth Occupation Force...
(AASC) and Australian Army Medical Corps
Royal Australian Army Medical Corps
The Royal Australian Army Medical Corps is the branch of the Australian Army responsible for providing medical care to Army personnel. The AAMC was formed in 1902 and has participated in every Australian Army operation...
(AAMC). In support were the sappers of the 2/7th Field Company and the 24 25-pounders of the 2/6th Field Regiment. In case Edgar got into trouble, the 20th Infantry Brigade
20th Brigade (Australia)
The 20th Brigade was a brigade-sized infantry unit of the Australian Army. The brigade was raised for service during the World War II on 7 May 1940 as part of the 7th Division. The brigade was transferred to the 9th Division in 1941...
was in reserve, on six hours notice.
To support the advance, a beach maintenance area was prepared at a beach at the mouth of the Kalueng River, which involved removing underwater and landward obstacles. So that the tanks and jeeps could immediately support the advance, a bridge was required over the Kalueng River. A preliminary operation by the 22nd Infantry Battalion on 3 December 1943 secured a crossing area and a log bridge was constructed. The operation jumped off on 5 December, with the 29th/46th Infantry Battalion passing through the bridgehead established by the 22nd. It soon came under sporadic enemy fire, and a tank was disabled by a land mine. In the face of mounting opposition, the advance was halted near the lagoon. It resumed the next day, and the Japanese withdrew after an artillery bombardment, their orders being "while avoiding any decisive engagement" to "carry out successful resistance to try to delay the enemy advance". This became the pattern, with the Japanese preferring to withdraw rather than suffer heavy casualties. On 10 December, Edgar brought all three of his battalions into the line and by 14 December they were closing in Lakona, a key position on the 20th Division's retreat route.
The tanks had difficulty keeping up with the advance. One obstacle was mines. On the first day, the 2/7th Field Company lifted fourteen mines but a tractor broke a track running over a mine. On 7 December, two more tanks were damaged by mines, one beyond repair. The sappers then cut a new track which they corduroyed
Corduroy road
A corduroy road or log road is a type of road made by placing sand-covered logs perpendicular to the direction of the road over a low or swampy area....
. To support the attack on Lakona, the tanks had to cross a creek with steep coral banks, swollen by a torrential downpour. While efforts were made to bring up a compressor, tanks fired into banks and holes were packed with explosives and detonated. On the evening of 16 December, the infantry were joined by five Matilda tanks, and the Japanese positions were overrun. Some 47 Japanese dead were counted; another 17 were killed in mopping-up operations the next day. On 20 December, aided by four Matilda tanks and 750 rounds from the 25-pounders, the 4th Infantry Brigade occupied the Fortification Point area. Between 5 and 20 December the 4th Infantry Brigade reported 65 killed and 136 wounded. Japanese casualties were 420 killed and 136 found dead, victims of disease, malnutrition and suicide. Only six Japanese prisoners were taken.
Sio
On 21 December 1943, the 20th Infantry Brigade passed through the 4th Infantry Brigade and initiated the second stage of the pursuit. Generals BlameyThomas Blamey
Field Marshal Sir Thomas Albert Blamey GBE, KCB, CMG, DSO, ED was an Australian general of the First and Second World Wars, and the only Australian to date to attain the rank of field marshal....
, Berryman and Wootten visited the acting brigade commander, Lieutenant Colonel
Lieutenant colonel
Lieutenant colonel is a rank of commissioned officer in the armies and most marine forces and some air forces of the world, typically ranking above a major and below a colonel. The rank of lieutenant colonel is often shortened to simply "colonel" in conversation and in unofficial correspondence...
N. W. Simpson, and emphasised that the brigade was to minimise casualties where possible by employing artillery and tanks. That afternoon, the lead company of the 2/13th Infantry Battalion reached Hubika. The battalion diarist recorded:
Christmas pudding
Christmas pudding is a pudding traditionally served on Christmas Day . It has its origins in medieval England, and is sometimes known as plum pudding or plum duff, though this can also refer to other kinds of boiled pudding involving dried fruit.-Basics:Many households have their own recipe for...
, and Christmas services were held. General Blamey insisted that Christmas fare be available to all units, and extraordinary efforts were made to carry out his directive. In one instance, a Piper Cub
Piper J-3
The Piper J-3 Cub is a small, simple, light aircraft that was built between 1937 and 1947 by Piper Aircraft. With tandem seating, it was intended for flight training but became one of the most popular and best-known light aircraft of all time...
of No. 4 Squadron RAAF
No. 4 Squadron RAAF
No. 4 Squadron is a Royal Australian Air Force squadron responsible for training forward air controllers. The squadron was previously a fighter and army co-operation unit active in both World War I and World War II.-World War I:...
dropped Christmas fare to a Papuan Company on a long range patrol. The advance resumed on 27 December, preceded by air strikes by 18 B-25 Mitchell
B-25 Mitchell
The North American B-25 Mitchell was an American twin-engined medium bomber manufactured by North American Aviation. It was used by many Allied air forces, in every theater of World War II, as well as many other air forces after the war ended, and saw service across four decades.The B-25 was named...
and 12 Boston bombers. The 2/15th Infantry Battalion and tanks of A Squadron, 1st Tank Battalion took the lead on 31 December; they reached Sialum on 2 January 1944. This had a sheltered beach which served a maintenance area. That day, the American landing at Saidor
Landing at Saidor
The Landing at Saidor was an Allied amphibious landing at Saidor, Papua New Guinea on 2 January 1944 as part of Operation Dexterity during World War II. In Allied hands, Saidor was a stepping stone towards Madang, the ultimate objective of General Douglas MacArthur's Huon Peninsula campaign...
placed a large force across the Japanese escape route.
Before moving over the mountains, the 20th Division headquarters elected to destroy its cryptographic materials rather than carry them. As the wet weather made burning them page by page a slow and difficult process, and a fire might attract the attention of the Allied Air Forces, someone decided to simply bury them in a steel trunk in a stream bed. An Australian sapper
Sapper
A sapper, pioneer or combat engineer is a combatant soldier who performs a wide variety of combat engineering duties, typically including, but not limited to, bridge-building, laying or clearing minefields, demolitions, field defences, general construction and building, as well as road and airfield...
checking the stream bed for booby traps with a metal detector
Metal detector
A metal detector is a device which responds to metal that may not be readily apparent.The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field...
discovered it, and it was dug up in the belief that it was a mine. An intelligence officer recognised the contents as code books and soon it was on its way to the Central Bureau
Central Bureau
The Central Bureau was one of two Allied Sigint organisations in the South West Pacific area during World War II. Central Bureau was attached to the HQ of the Allied Commander of the South West Pacific area, Douglas MacArthur. The other unit was the joint RAN/USN Fleet Radio Unit, Melbourne ,...
in Brisbane
Brisbane
Brisbane is the capital and most populous city in the Australian state of Queensland and the third most populous city in Australia. Brisbane's metropolitan area has a population of over 2 million, and the South East Queensland urban conurbation, centred around Brisbane, encompasses a population of...
. There, the pages were carefully dried out and photographed. On 4 February 1944, Central Bureau codebreakers decrypted a thirteen-part message that laid out the decisions reached at a conference of high ranking Japanese officers. Copies of the material were quickly sent to Arlington Hall
Arlington Hall
Arlington Hall was a former girl's school and the headquarters of the US Army's Signal Intelligence Service cryptography effort during World War II. The site presently houses the George P. Shultz National Foreign Affairs Training Center, and the United States National Guard Readiness Center. It...
. In January 1944, Arlington Hall had decrypted 1,846 Japanese army messages. In March 1944, with the Sio code books in hand, it decrypted 36,000 messages.
On 11 January a platoon of the 2/17th Infantry Battalion
2/17th Battalion (Australia)
The 2/17th Battalion was an infantry battalion of the Australian Army. Raised in April 1940 in New South Wales, the unit saw service in the Middle East in 1941–42, taking part in the fighting at Tobruk and El Alamein before returning to Australia early in 1943. In 1943–44 the battalion fought in...
replaced a rope ladder, and after climbing it and two wooden ladders reached an area atop a cliff which had once been a Japanese headquarters. It would have been a formidable position if defended, but it was not. The main body of the battalion followed the next day. The Goaling River was crossed in small boats left behind by the Japanese on 13 January and it entered Nambariwa, where one prisoner was taken, six Japanese were shot, and nine found dead. On 15 January, Sio was taken. The Sio-Nambariwa area was found to have been the principal Japanese supply area, and a large number of fuel, supply, and stores dumps were found. During the advance from Fortification Point to Sio, 303 Japanese had been killed or found dead, and 22 captured. The 20th Infantry Brigade had lost 3 killed and 13 wounded, but 958 had been evacuated sick, mostly with malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
, but an epidemic of dengue had also taken its toll. Large quantities of Japanese equipment had been captured, including six 75 mm guns
Type 41 75 mm Mountain Gun
The Type 41 75 mm mountain gun is a Japanese license-built copy of the Krupp M.08 mountain gun. Originally it was the standard pack artillery weapon. After it was superseded by the Type 94 75 mm mountain gun, it was then used as an infantry "regimental" gun, deployed 4 to each infantry...
, three 37 mm guns
Type 11 37 mm Infantry Gun
The was an infantry support gun used by the Imperial Japanese Army in the Second Sino-Japanese War and World War II.-History and development:The Type 11 infantry gun entered service in 1922...
and three 20 mm guns
Type 2 20 mm AA Machine Cannon
The Type 2 20 mm AA Machine Cannon was a Japanese-designed anti-aircraft gun, based on the German Flak 38. It entered service in 1942. A central fire-control system was developed for Type 2, which could control and direct 6 of the guns at once....
.
Saidor
Lae
Lae, the capital of Morobe Province, is the second-largest city in Papua New Guinea. It is located at the start of the Highlands Highway which is the main land transport corridor from the Highlands region to the coast...
, replaced that of the 9th Division. At the same time the 8th Infantry Brigade
8th Brigade (Australia)
8th Brigade is an Australian Army Reserve combined-arms formation stationed in New South Wales.The 8th Brigade is one of six brigades of the Australian Army's 2nd Division, and includes units and personnel from all Armoured, Infantry, Artillery, Engineers, Signals, Ordinance , Medical, Nursing,...
replaced the 20th. This formation, which had spent much of the war on garrison duty in Western Australia, had begun departing Cairns on 10 January. The original intention had been for this brigade to go to Lae to relieve the 29th Infantry Brigade, which had fought in the Salamaua-Lae campaign
Salamaua-Lae campaign
The Salamaua–Lae campaign was a series of actions in the New Guinea campaign of World War II. Australian and United States forces sought to capture two major Japanese bases, one in the town of Lae, and another one at Salamaua. The campaign to take the Salamaua and Lae area began with the Australian...
, but in December it was decided to ship the 8th Infantry Brigade direct to Finschhafen. The brigade contained three infantry battalions, the 4th, 30th
30th Battalion (Australia)
The 30th Battalion was an infantry battalion of the Australian Army. It was originally formed in 1915 during the First World War and saw service on the Western Front before being disbanded in 1919. It was re-raised in 1921 but was later amalgamated with the 51st Battalion in 1930. In 1935 the two...
and 35th
35th Battalion (Australia)
The 35th Battalion was an infantry battalion of the Australian Army. Originally raised in late 1915 for service during the First World War, the battalion saw service on the Western Front in France and Belgium before being disbanded in 1919. In 1921 it was re-raised in the Newcastle region of New...
, all from New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
. It also still had the support of the 2/12th Field Regiment, 532nd EBSR, and A Company, Papuan Infantry Battalion. The brigade suffered its first casualties on the night of 21/22 January in a friendly fire
Friendly fire
Friendly fire is inadvertent firing towards one's own or otherwise friendly forces while attempting to engage enemy forces, particularly where this results in injury or death. A death resulting from a negligent discharge is not considered friendly fire...
incident, which was a common occurrence with units inexperienced in jungle warfare
Jungle warfare
Jungle warfare is a term used to cover the special techniques needed for military units to survive and fight in jungle terrain.It has been the topic of extensive study by military strategists, and was an important part of the planning for both sides in many conflicts, including World War II and the...
. Two Australians were killed and two wounded by their own comrades.
On 22 January a native reported seeing seven Japanese in the hills south west of Sio and a patrol was sent out under Corporal
Corporal
Corporal is a rank in use in some form by most militaries and by some police forces or other uniformed organizations. It is usually equivalent to NATO Rank Code OR-4....
Bengari to investigate. On arriving in the vicinity on 24 January, a local reported that another 22 Japanese had arrived. The next morning, Bengari and his five companions ambushed the Japanese and killed them all before they could fire a shot. Wirraway
CAC Wirraway
The Wirraway was a training and general purpose military aircraft manufactured in Australia by the Commonwealth Aircraft Corporation between 1939 and 1946...
and Boomerang
CAC Boomerang
The CAC Boomerang was a World War II fighter aircraft designed and manufactured in Australia between 1942 and 1945. The Commonwealth Aircraft Corporation produced Boomerangs under the production contract numbers CA-12, CA-13, CA-14 and CA-19, with aircraft supplied under each subsequent contract...
aircraft of No. 4 Squadron RAAF scouted ahead of the advance. Its aerial reconnaissance work let the Australians and Papuans know where opposition could be expected, thereby speeding up the advance. The pilots noted Japanese parachutes, signs that the Japanese were receiving supplies by air. On 4 February, the Australians were also forced onto air supply, as swollen rivers washed out a number of bridges.
Each day the Papuans killed 12 to 15 Japanese, but not until 8 February was the Japanese rearguard encountered at Weber Point and a formal attack made. Five Japanese were killed. In all, 53 Japanese were killed and four captured that day. Two Australians were wounded. The next day another 61 Japanese were killed and 9 captured, this time without any Australian casualties. On 10 February, the 30th Infantry Battalion encountered two American soldiers at Yagomai, thereby linking up with the American force at Saidor.
The 8th Infantry Brigade now began to mop up the area. On 18 February, the 35th Infantry Battalion attacked a Japanese force near Gabutamon, killing 40. Finding a force of about 100 Japanese at nearby Tapen, they attacked, killing another 52 Japanese for the loss of one man wounded, while the Papuans on their flanks killed another 51, of whom 43 were accounted for by Corporal Bengali and two other Papuans. The next day, the Papuans found and killed another 39 Japanese in the vicinity. At Tapen, the Australians and Papuans also found evidence that the Japanese had resorted to cannibalism
Cannibalism
Cannibalism is the act or practice of humans eating the flesh of other human beings. It is also called anthropophagy...
. In the period 20 January – 1 March 1944, 734 Japanese were killed, 1,775 found dead and 48 were captured. Australian casualties came to four killed and six wounded.
Aftermath
Both sides managed to accomplish their objectives; the Japanese managed to withdraw, while the Australians exacted a terrible toll. The balance of losses was overwhelmingly against the Japanese, both in terms of men and equipment. It seems that only about 4,300 of the 7,000 troops under the command of the Japanese 20th Division20th Division (Imperial Japanese Army)
was an infantry division in the Imperial Japanese Army. Its call sign was the .-History:The 20th Division and the 19th Division were raised on 24 December 1915 as a garrison force for Korea. After Japan's victory in the Russo-Japanese War, and subsequent occupation, and then annexation of Korea,...
that had originally been forward of Sio survived the withdrawal, and many of them were rendered ineffective through wounds, sickness, malnutrition and exhaustion. However, the opportunity to destroy the Japanese 51st Division
51st Division (Imperial Japanese Army)
The 51st Division was an infantry division of the Imperial Japanese Army. It was formed on 10 July 1940 at Utsunomiya, Tochigi, and was assigned to the Eastern District Army. Under the command of Lieutenant General Kenichiro Ueno, upon formation the division's infantry group consisted of three...
was not seized. These troops would live to fight the Americans at the Battle of Driniumor River
Battle of Driniumor River
The Battle of Driniumor River, also known as The Battle of Aitape, 10 July – 25 August 1944, was part of the Western New Guinea campaign of World War II. Japanese forces attacked United States forces on the Driniumor River, near Aitape in New Guinea...
later in the year, and the Australians in the Aitape–Wewak campaign in 1945. On the other hand, the new base at Finschhafen was no longer threatened by the Japanese, and would became an important staging point for the Western New Guinea campaign
Western New Guinea campaign
The Western New Guinea campaign was a series of actions in the New Guinea campaign of World War II. United States and Australian forces assaulted Japanese bases and positions in the northwest coastal areas of Netherlands New Guinea and adjoining parts of the Australian Territory of New Guinea...
. The capture of the Japanese ciphers at Sio would allow General MacArthur to carry out Operations Reckless and Persecution
Operations Reckless and Persecution
Operation Reckless, known as the Landing at Hollandia and Operation Persecution known as the Aitape landing, were Allied amphibious landings which commenced the Western New Guinea campaign. Both operations commenced on 22 April 1944....
with a plan based upon sound intelligence rather than just his own intuition.