Operation Mo
Encyclopedia
Operation Mo or the Port Moresby Operation was the name of the Japanese
Empire of Japan
The Empire of Japan is the name of the state of Japan that existed from the Meiji Restoration on 3 January 1868 to the enactment of the post-World War II Constitution of...

 plan to take control of the Australian Territory of New Guinea
Territory of New Guinea
The Territory of New Guinea was the Australia-controlled, League of Nations-mandated territory in the north eastern part of the island of New Guinea, and surrounding islands, between 1920 and 1949...

 during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 as well as other locations in the South Pacific
Oceania
Oceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...

 with the goal of isolating Australia and New Zealand from their ally
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 the United States. The plan was developed by the Imperial Japanese Navy
Imperial Japanese Navy
The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...

 and supported by Admiral Isoroku Yamamoto
Isoroku Yamamoto
was a Japanese Naval Marshal General and the commander-in-chief of the Combined Fleet during World War II, a graduate of the Imperial Japanese Naval Academy and a student of Harvard University ....

, the commander-in-chief of the Combined Fleet. The operation failed.

Japanese Navy interest in Operation Mo

During the Japanese Navy's planning of their 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:...

 (air strikes against Lae
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...

 and Salamaua
Salamaua
Salamaua was a small town situated on the north-eastern coastline of Papua New Guinea part of Morobe province. The settlement was built on a minor isthmus between the coast with mountains on the inland side and a headland...

, disembarkation in Huon Gulf
Huon Gulf
Huon Gulf is a large gulf in eastern Papua New Guinea, at . It is bordered by Huon Peninsula in the north. Both are named after French explorer Jean-Michel Huon de Kermadec. Huon Gulf is a part of the Solomon Sea. Lae, capital of the Morobe Province is located on the northern coast of the...

, New Britain (Rabaul
Rabaul
Rabaul is a township in East New Britain province, Papua New Guinea. The town was the provincial capital and most important settlement in the province until it was destroyed in 1994 by falling ash of a volcanic eruption. During the eruption, ash was sent thousands of metres into the air and the...

), New Ireland (Kavieng
Kavieng
Kavieng is the capital of the Papua New Guinean province of New Ireland and the largest town on the island of the same name. The town is located at Balgai Bay, on the northern tip of the island. As of 2000, it had a population of 10,600....

), Finch Harbor (also called Finschhafen), and the capture of Morobe
Morobe
Morobe may refer to several places in Papua New Guinea:*Morobe Province*Morobe, Papua New Guinea*Morobe Goldfield *Morobe Bay...

 and Buna
Buna, Papua New Guinea
Buna is a village in Oro Province, Papua New Guinea. It was the site in part, of the Battle of Buna-Gona during World War II, when it constituted a variety of native huts and a handful of houses with a airstrip...

), it envisioned those territories as support points to implement the capture of Port Moresby
Port Moresby
Port Moresby , or Pot Mosbi in Tok Pisin, is the capital and largest city of Papua New Guinea . It is located on the shores of the Gulf of Papua, on the southeastern coast of the island of New Guinea, which made it a prime objective for conquest by the Imperial Japanese forces during 1942–43...

. The implementation of these operations was assigned to the Japanese Naval task force led by Admiral
Admiral
Admiral is the rank, or part of the name of the ranks, of the highest naval officers. It is usually considered a full admiral and above vice admiral and below admiral of the fleet . It is usually abbreviated to "Adm" or "ADM"...

 Chūichi Nagumo
Chuichi Nagumo
was a Japanese admiral in the Imperial Japanese Navy during World War II and one time commander of the Kido Butai . He committed suicide during the Battle of Saipan.-Early life:...

, after completing the Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...

 campaign. Another important step was the occupation of Christmas Island
Christmas Island
The Territory of Christmas Island is a territory of Australia in the Indian Ocean. It is located northwest of the Western Australian city of Perth, south of the Indonesian capital, Jakarta, and ENE of the Cocos Islands....

 to the south of Java. The Japanese Navy General Staff had been considering Operation Mo since 1938, as a step in the consolidation of the Southern Seas areas in the Greater East Asia Co-Prosperity Sphere
Greater East Asia Co-Prosperity Sphere
The Greater East Asia Co-Prosperity Sphere was a concept created and promulgated during the Shōwa era by the government and military of the Empire of Japan. It represented the desire to create a self-sufficient "bloc of Asian nations led by the Japanese and free of Western powers"...

 (大東亜共栄圏 Dai-tō-a Kyōeiken).

Strategic lines in Operation Mo

The Directive of Operation Mo was conceived in 1938, but with no specific time for its execution, pending earlier successes in the southern area during the first and second phases of the conquest.

In April 1942, the operation was organized into four large actions and was approved by the Army and Navy General Staffs:
  • On 3 May, the Light Task Force occupied the port of Tulagi
    Tulagi
    Tulagi, less commonly Tulaghi, is a small island in the Solomon Islands, just off the south coast of Florida Island. The town of the same name on the island Tulagi, less commonly Tulaghi, is a small island (5.5 km by 1 km) in the Solomon Islands, just off the south coast of Florida...

    , near Guadalcanal
    Guadalcanal
    Guadalcanal is a tropical island in the South-Western Pacific. The largest island in the Solomons, it was discovered by the Spanish expedition of Alvaro de Mendaña in 1568...

     in the Solomon Islands
    Solomon Islands
    Solomon Islands is a sovereign state in Oceania, east of Papua New Guinea, consisting of nearly one thousand islands. It covers a land mass of . The capital, Honiara, is located on the island of Guadalcanal...

    , to establish a seaplane
    Seaplane
    A seaplane is a fixed-wing aircraft capable of taking off and landing on water. Seaplanes that can also take off and land on airfields are a subclass called amphibian aircraft...

     base and a base for operations in the Coral Sea
    Coral Sea
    The Coral Sea is a marginal sea off the northeast coast of Australia. It is bounded in the west by the east coast of Queensland, thereby including the Great Barrier Reef, in the east by Vanuatu and by New Caledonia, and in the north approximately by the southern extremity of the Solomon Islands...

     area. The same force was to take Nauru
    Nauru
    Nauru , officially the Republic of Nauru and formerly known as Pleasant Island, is an island country in Micronesia in the South Pacific. Its nearest neighbour is Banaba Island in Kiribati, to the east. Nauru is the world's smallest republic, covering just...

     and Banaba Island
    Banaba Island
    Banaba Island , an island in the Pacific Ocean, is a solitary raised coral island west of the Gilbert Island chain and 300 km east of Nauru. It is part of the Republic of Kiribati. It has an area of 6.5 km², and the highest point on the island is also the highest point in Kiribati, at 81...

     (Ocean Island) for their valuable phosphate
    Phosphate
    A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

     deposits.

  • The South Seas Detachment
    South Seas Detachment
    The South Seas Detachment of the Imperial Japanese Army was a brigade-size force formed in 1941 to be the army unit used in the Japanese seizure of the South Pacific island groups of Wake, Guam and the Gilberts. As part of the South Seas Force, it fell under Imperial Japanese Navy command and...

     was to disembark in Port Moresby
    Port Moresby
    Port Moresby , or Pot Mosbi in Tok Pisin, is the capital and largest city of Papua New Guinea . It is located on the shores of the Gulf of Papua, on the southeastern coast of the island of New Guinea, which made it a prime objective for conquest by the Imperial Japanese forces during 1942–43...

     on 7 May, with another force occupying territory in the Louisiade Archipelago
    Louisiade Archipelago
    The Louisiade Archipelago is a string of ten larger volcanic islands frequently fringed by coral reefs, and 90 smaller coral islands located 200 km southeast of New Guinea, stretching over more than and spread over an ocean area of between the Solomon Sea to the north and the Coral Sea to...

     for another seaplane base.

  • Another objective of the South Sea Detachment was the assault on New Caledonia
    New Caledonia
    New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...

    , Fiji
    Fiji
    Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...

    , and Samoa
    Samoa
    Samoa , officially the Independent State of Samoa, formerly known as Western Samoa is a country encompassing the western part of the Samoan Islands in the South Pacific Ocean. It became independent from New Zealand in 1962. The two main islands of Samoa are Upolu and one of the biggest islands in...

    . IGHQ assigned a new double objective: capture and secure Port Moresby, in cooperation with the Navy; and seize strategic points of opportunity in eastern New Guinea
    New Guinea
    New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

    .

  • Another important Naval force, departing from Truk, was to pass the Eastern Solomons area to the south, finally advancing toward the west in order to intercept the enemy. Following this, strikes were planned on the coastal cities of Coen
    Coen, Queensland
    Coen is a small inland town on the main road heading up the Cape York Peninsula in far northern Queensland, Australia. It is in the Cook Shire Local Government Area. At the 2006 census, Coen had a population of 253....

    , Cooktown
    Cooktown, Queensland
    Cooktown is a small town located at the mouth of the Endeavour River, on Cape York Peninsula in Far North Queensland where James Cook beached his ship, the Endeavour, for repairs in 1770. At the 2006 census, Cooktown had a population of 1,336...

     and Townsville
    Townsville, Queensland
    Townsville is a city on the north-eastern coast of Australia, in the state of Queensland. Adjacent to the central section of the Great Barrier Reef, it is in the dry tropics region of Queensland. Townsville is Australia's largest urban centre north of the Sunshine Coast, with a 2006 census...

     in Queensland, which were terminal points in the supply line between the United States and Australia. The final object was Thursday Island to the north of Cape York
    Cape York Peninsula
    Cape York Peninsula is a large remote peninsula located in Far North Queensland at the tip of the state of Queensland, Australia, the largest unspoilt wilderness in northern Australia and one of the last remaining wilderness areas on Earth...

    .

  • The Japanese had one Air Naval land-based fleet detached in Rabaul
    Rabaul
    Rabaul is a township in East New Britain province, Papua New Guinea. The town was the provincial capital and most important settlement in the province until it was destroyed in 1994 by falling ash of a volcanic eruption. During the eruption, ash was sent thousands of metres into the air and the...

    , Lae
    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...

    , Salamaua
    Salamaua
    Salamaua was a small town situated on the north-eastern coastline of Papua New Guinea part of Morobe province. The settlement was built on a minor isthmus between the coast with mountains on the inland side and a headland...

     and Buna
    Buna, Papua New Guinea
    Buna is a village in Oro Province, Papua New Guinea. It was the site in part, of the Battle of Buna-Gona during World War II, when it constituted a variety of native huts and a handful of houses with a airstrip...

    . This Air fleet executed the air strikes against Port Moresby
    Port Moresby
    Port Moresby , or Pot Mosbi in Tok Pisin, is the capital and largest city of Papua New Guinea . It is located on the shores of the Gulf of Papua, on the southeastern coast of the island of New Guinea, which made it a prime objective for conquest by the Imperial Japanese forces during 1942–43...

     on 5 May and 6 May, in preparation for the Japanese landing on 7 May.

Japanese countermeasures against Allied response

Japanese planners took into account an Allied response to the operation by detaching one task force to the west of parallel between of Rennel and Deboyne Islands and another to the east of same point. These measures would permit a Japanese invasion force to use the Jomard Passage directly to Port Moresby
Port Moresby
Port Moresby , or Pot Mosbi in Tok Pisin, is the capital and largest city of Papua New Guinea . It is located on the shores of the Gulf of Papua, on the southeastern coast of the island of New Guinea, which made it a prime objective for conquest by the Imperial Japanese forces during 1942–43...

.

Japanese naval intelligence also suspected the presence of the American aircraft carrier
Aircraft carrier
An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations...

  in Coral Sea
Coral Sea
The Coral Sea is a marginal sea off the northeast coast of Australia. It is bounded in the west by the east coast of Queensland, thereby including the Great Barrier Reef, in the east by Vanuatu and by New Caledonia, and in the north approximately by the southern extremity of the Solomon Islands...

 waters during this period.

Proposed Japanese forces

The Tulagi assault force was composed of the following units:
  • Minelayer-cruiser
  • Seaplane tender Kiyokawa Maru
  • Destroyers Kikutsuki, Minatsuki, Mochitsuki and Yuziki
  • two transports
  • smaller support vessels


The Port Moresby occupation force was composed of the following units:
  • Light cruisers , Mutzuki, Yagoi, Uzuki, Asanagi, Oite and Yunagi
  • Minelayer
    Minelayer
    Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, since World War I the term minelayer refers specifically to a naval ship used for deploying naval mines...

    s and sea patrol vessels
  • Seaplane tender
  • Minelayer


Supporting these operations and intercepting any Allied interference, Rear Admiral Aritomo Goto
Aritomo Goto
was an admiral in the Imperial Japanese Navy during World War II.-Early career:Gotō was born in Ibaraki prefecture in 1888. He graduated from the 38th class of the Imperial Japanese Naval Academy in 1910, ranked 30th out of a class of 149 cadets. As a midshipman, he served on the cruiser and...

 commanded:
  • Light carrier
  • Heavy cruisers , , and
  • Light cruisers ,
  • Destroyer

During the course of operation, Yamamoto
Isoroku Yamamoto
was a Japanese Naval Marshal General and the commander-in-chief of the Combined Fleet during World War II, a graduate of the Imperial Japanese Naval Academy and a student of Harvard University ....

 sent the following heavy support force from Truk, led by Rear Admiral Chuichi Hara
Chuichi Hara
-External links:*...

:
  • Fleet carriers and
  • Heavy cruisers and
  • Destroyers , , , , and
  • Auxiliary vessels


Supporting this force was the 25th Air Fleet, (Yokohama Air Corps) led by Rear Admiral Sadayoshi Yamada
Sadayoshi Yamada
- Notes :...

, based in Rabaul
Rabaul
Rabaul is a township in East New Britain province, Papua New Guinea. The town was the provincial capital and most important settlement in the province until it was destroyed in 1994 by falling ash of a volcanic eruption. During the eruption, ash was sent thousands of metres into the air and the...

, Lae
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...

, Salamaua
Salamaua
Salamaua was a small town situated on the north-eastern coastline of Papua New Guinea part of Morobe province. The settlement was built on a minor isthmus between the coast with mountains on the inland side and a headland...

, Buna
Buna, Papua New Guinea
Buna is a village in Oro Province, Papua New Guinea. It was the site in part, of the Battle of Buna-Gona during World War II, when it constituted a variety of native huts and a handful of houses with a airstrip...

 and Deboyne island, composed of 60 Mitsubishi A6M "Zero" fighters, 48 Mitsubishi G3M
Mitsubishi G3M
The Mitsubishi G3M was a Japanese bomber used during World War II.-Design and development:...

 "Nell" and 26 Aichi E13A
Aichi E13A
-See also:-References:NotesBibliography* Dorr, Robert E. and Chris Bishop. Vietnam Air War Debrief. London: Aerospace Publishing, 1996. ISBN 1-874023-78-6....

 "Jake" and Mitsubishi F1M
Mitsubishi F1M
-See also:-Bibliography:* Francillon, R.J. Japanese Aircraft of the Pacific War. London:Putnam, 1970. ISBN 370 00033 1.* Green, William. War Planes of the Second World War, Volume Six: Floatplanes. London: Macdonald & Co., Ltd., 1962....

 "Pete" reconnaissance seaplanes. This unit bombed Port Moresby
Port Moresby
Port Moresby , or Pot Mosbi in Tok Pisin, is the capital and largest city of Papua New Guinea . It is located on the shores of the Gulf of Papua, on the southeastern coast of the island of New Guinea, which made it a prime objective for conquest by the Imperial Japanese forces during 1942–43...

 on 5–6 May, ahead of the Japanese Army-Navy landing on 7 May.

Actual development of Operation Mo

The Tulagi assault force began their landings on Tulagi on 3 May. On 4 May 1942, troopships bearing the South Seas Detachment
South Seas Detachment
The South Seas Detachment of the Imperial Japanese Army was a brigade-size force formed in 1941 to be the army unit used in the Japanese seizure of the South Pacific island groups of Wake, Guam and the Gilberts. As part of the South Seas Force, it fell under Imperial Japanese Navy command and...

 set sail southward from Rabaul
Rabaul
Rabaul is a township in East New Britain province, Papua New Guinea. The town was the provincial capital and most important settlement in the province until it was destroyed in 1994 by falling ash of a volcanic eruption. During the eruption, ash was sent thousands of metres into the air and the...

 for Port Moresby
Port Moresby
Port Moresby , or Pot Mosbi in Tok Pisin, is the capital and largest city of Papua New Guinea . It is located on the shores of the Gulf of Papua, on the southeastern coast of the island of New Guinea, which made it a prime objective for conquest by the Imperial Japanese forces during 1942–43...

. This same day US aircraft from Yorktown attacked the Tulagi assault force, inflicting heavy damage, but were unsuccessful in preventing the occupation of Tulagi, Gavutu, and Tanambogo islands. Three days later, as a naval engagement appeared to be brewing in the Coral Sea
Coral Sea
The Coral Sea is a marginal sea off the northeast coast of Australia. It is bounded in the west by the east coast of Queensland, thereby including the Great Barrier Reef, in the east by Vanuatu and by New Caledonia, and in the north approximately by the southern extremity of the Solomon Islands...

, the Japanese Moresby transports immediately veered back to the north, in order to avoid combat. The resulting Battle of the Coral Sea
Battle of the Coral Sea
The Battle of the Coral Sea, fought from 4–8 May 1942, was a major naval battle in the Pacific Theater of World War II between the Imperial Japanese Navy and Allied naval and air forces from the United States and Australia. The battle was the first fleet action in which aircraft carriers engaged...

 inflicted significant aircraft losses on the Fourth Fleet
Fourth Fleet
Fourth Fleet or 4th fleet may mean:* United States Fourth Fleet* IJN 4th Fleet, Imperial Japanese Navy* Luftflotte 4-See also:* Fourth * Fleet * Third Fleet * Fifth Fleet...

, Shōhō was sunk, and Shōkaku was damaged.

The Japanese abandoned their plans to land the South Seas Detachment directly at Port Moresby from the sea. The Japanese Army was making new preparations for combat when, on 11 July, High Command ordered the suspension of the projected actions against New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...

, Fiji
Fiji
Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...

, and Samoa
Samoa
Samoa , officially the Independent State of Samoa, formerly known as Western Samoa is a country encompassing the western part of the Samoan Islands in the South Pacific Ocean. It became independent from New Zealand in 1962. The two main islands of Samoa are Upolu and one of the biggest islands in...

, because the Combined Fleet
Combined Fleet
The was the main ocean-going component of the Imperial Japanese Navy. The Combined Fleet was not a standing force, but a temporary force formed for the duration of a conflict or major naval maneuvers from various units normally under separate commands in peacetime....

 was defeated at Midway
Battle of Midway
The Battle of Midway is widely regarded as the most important naval battle of the Pacific Campaign of World War II. Between 4 and 7 June 1942, approximately one month after the Battle of the Coral Sea and six months after Japan's attack on Pearl Harbor, the United States Navy decisively defeated...

.

These battles prevented the Japanese landings against Port Moresby. Instead the Japanese army commenced an ultimately unsuccessful campaign to take Port Moresby with an overland approach across the Owen Stanley Range
Owen Stanley Range
Owen Stanley Range is the south-eastern part of the central mountain-chain in Papua New Guinea. It was seen in 1849 by Captain Owen Stanley while surveying the south coast of Papua and named after him. Strictly, the eastern extremity of the range is Mount Victoria , which was climbed by Sir William...

 via the Kokoda Track
Kokoda Track campaign
The Kokoda Track campaign or Kokoda Trail campaign was part of the Pacific War of World War II. The campaign consisted of a series of battles fought between July and November 1942 between Japanese and Allied—primarily Australian—forces in what was then the Australian territory of Papua...

.
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