Auxiliary ship Olterra
Encyclopedia
The auxiliary ship Olterra was a 5,000 tons Italian tanker scuttled by her own crew at Algeciras
bay on 10 June 1940, after the entry of Italy in World War II. She was recovered in 1942 by a special unit of the Decima Flottiglia MAS
to be used as an undercover base for manned torpedoes
in order to attack Allied shipping at Gibraltar
.
; the other two were the work of combat swimmers.
Five merchant ships were sunk or damaged from July to September 1942 by frogmen using limpet mines. The Olterra played the role of advanced observation post for those missions.
to watch the Bay of Algeciras and the Allied ships at anchor there. A scene of civilian sailors working to overhaul the ship was meanwhile set up for the outsiders, in order to deceive both British and Spanish authorities. The torpedoes (in spare parts) and other equipment were smuggled into Spain by men of the Decima under the pretense of being materials for the ‘works’ on board the Olterra. Finally, a sliding hatch was open with a cutting torch six feet below the waterline. This would be the exit door of the manned torpedoes, which would launch their attacks from the flooding bilge
, right beneath the workshop. The special unit in charge of the operations was dubbed Squadriglia Ursa Major, after the constellation of the same name
.
, a naval squadron consisting of the battleship HMS Nelson, the battle cruiser HMS Renown
, the aircraft-carriers HMS Furious
and HMS Formidable and a number of escort units entered Gibraltar. Visintini planned a three manned torpedoes mission, each of them carrying 2 divers: the leading torpedo, driven by Visintini himself and Petty Officer Magro, the second by 2nd Lieutenant Cella and Sergeant Leone and the third by Midshipman Manisco and Petty Officer Varini. The targets were designated in the following order: for Visintini, Nelson, for Manisco, Formidable and for Cella, Furious.
The assault craft departed from the Olterra during the early hours of 8 December. At 2:15 AM, the first human torpedo reached the area of the boom defences. The motor launches and sentries inside the British base were quietly active and alert, conscious of the danger of a potential attack on the fleet at anchor. One of the security measures taken by the Royal Navy after the summer incursions of combat swimmers was the deployment at Gibraltar of an underwater bomb disposal unit, under the command of Lieutenant Lionel Crabb
. A pattern of depth charges was dropped by the motor barges at an interval of three minutes between each one. The craft of Visintini and Magro was apparently hit by one of the charges and destroyed when they were trying to find a breach in the steel net protecting the harbour. Their bodies were recovered by the British some days later and buried at sea with full honors. The second “pig” also endured the strong response of British defences after being uncovered by a searchlight. After an endless chase by anti-submarine boats, the Italian crew decided to scuttle their craft and took shelter on board an American freighter. They discarded their swimsuits before submitting themselves to Gibraltar authorities. The last manned torpedo was caught in the middle of the general alarm across the stronghold, but managed to slip beneath the waters and fool the submarine chasers. The copilot, Leone, became missing during the pursuit and was never found; Cella, meanwhile, abandoned the craft elsewhere, thinking that he was still near Gibraltar or, in the best case, stranded close to the Spanish coast. With the idea of becoming a prisoner of war or being arrested and interned by Spanish authorities in mind, Cella surfaced, only to find that he was just a few meters away from the Olterra. His torpedo was recovered by the Italians the following day. The two divers captured by the British told their interrogators that the attack was launched by submarine, successfully deceiving Allied intelligence. Nevertheless, the first human torpedoes mission ended in failure.
After the death of Visintini, Lieutenant Ernesto Notari took charge of the Ursa Major unit onboard the Olterra. Replacements of personnel and materials were also sent from Italy. Owing to the improvements in the boom defenses, the next missions were planned against transport and cargo ships in the anchorage area around the naval base. The end of the war in North Africa and the subsequent Allied landings on Sicily
also made the attacks on logistic ships a priority. In May 1943, Commander Borghese
, of Scire, was appointed commander of the Decima. The night of the 8th was chosen for the next assault, taking advantage of the bad weather and the phase of the moon. Lieutenant Notari, along with his second, Petty Officer Ario Lazzari, was the head of another three-"pig" wave heading for Gibraltar. The second human torpedo was manned by Lieutenant Tadini and Petty Officer Mattera, and the third by Second Lieutenant Cella and Petty Officer Montalenti. In order to divert any British suspicion from the Olterra, the selected targets were merchant ships at anchor in the farthest point from Algeciras. The gale that was raging at the time hampered the mission, because the current forced them to dive around the targets before they could attach the limpet mines to the hulls. At dawn, all the Italian craft reached their mother ship safely. They had mined three vessels, the American Liberty ship
Pat Harrison (7,000 tons), and the British freighters Mahsud (7,500 tons) and Camerata (4,875 tons). When the charges exploded, the American transport was heavily damaged and became a total loss. One American sailor was killed by the blast. The Mahsud rested on the bay’s bottom with much of the ship still above the water line, while the Camerata sank outright. To mislead the British into thinking of combat swimmers instead of manned torpedoes, members of the Italian secret service scattered diving equipment along the shore. The second attempt from the Olterra had been a stunning success.
On 25 July, Mussolini was removed from power, a clear signal that Italy was on the brink of collapse. The course of the war and the political changes were no deterrent for the Decima MAS, which continued to plan and execute attacks on Allied shipping in all fronts. On 10 June, the unit was awarded the Medaglia d’oro as a tribute to their deeds. On the night of 3 August 1943, the Ursa Maior carried out the last operation against the "Rock". Again, three craft left the Olterra in search of their targets: three transport ships at anchor in the bay. Notari led the "pigs" close to the Spanish coast to avoid the searchlights aimed at open sea. His second man was Petty Officer Giannoli, whose training on piloted torpedoes was poor. While the crew was clamping the explosive charge to the keel of a Liberty ship, their torpedo spun out of control. Notari opened the diving valves, and the "pig" suddenly crash dive
d to a depth of 34 meters. Then, the craft surfaced just a few feet from their intended victim. Half conscious and with no trace of his companion, Notari tried to fix the mechanical problems developed by his torpedo, but the diving mechanism was disabled. At the end, he managed to sneak out at full speed, helped by a flock of porpoises which covered his wake. Giannoli was left behind. After waiting two hours on the rudder of the ship, he shouted for help. Once Giannoli was taken on board, a motor launch carrying a member of Crabb’s diving unit was called to the scene. There was little doubt that the ship, the American Harrison Grey Otis had been mined. The warhead blew up just seconds before the British diver, Petty Officer Bell, could put his foot on the water. One sailor died and eight others were seriously injured. Like her sister ship Pat Harrison in May, the 7,700 tn Otis was declared a constructive total loss. Two other Allied ships were also rocked by explosions at the same time, about 4:00 am of 4 August. The Norwegian Thorshøvdi, of 9,900 tn was broken in two by the blast, while the British Stanridge (6,000 tons) sank in shallow water. The last mission of the Ursa Major destroyed 23,000 tn of Allied shipping.
's words:
The Spanish authorities tried to hide the evidence, but when Crabb’s diving team boarded the Olterra after the armistice, they found spare parts from three different torpedoes. This allowed them to reassemble a full manned torpedo, named Emily. The craft was lost after six trials at open seas. Crabb met some of his former enemies after the war, including the last commander of the Ursa Major, Lieutenant Notari.
Algeciras
Algeciras is a port city in the south of Spain, and is the largest city on the Bay of Gibraltar . Port of Algeciras is one of the largest ports in Europe and in the world in three categories: container,...
bay on 10 June 1940, after the entry of Italy in World War II. She was recovered in 1942 by a special unit of the Decima Flottiglia MAS
Decima Flottiglia MAS
The Decima Flottiglia MAS was an Italian commando frogman unit of the Regia Marina created during the Fascist regime.The acronym MAS also refers to various light torpedo boats used by the Regia Marina during World...
to be used as an undercover base for manned torpedoes
Human torpedo
Human torpedoes or manned torpedoes are a type of rideable submarine used as secret naval weapons in World War II. The basic design is still in use today; they are a type of diver propulsion vehicle....
in order to attack Allied shipping at Gibraltar
Gibraltar
Gibraltar is a British overseas territory located on the southern end of the Iberian Peninsula at the entrance of the Mediterranean. A peninsula with an area of , it has a northern border with Andalusia, Spain. The Rock of Gibraltar is the major landmark of the region...
.
Previous operations
From 24 September 1940 to 15 September 1942, there were six submarine-borne assaults on Gibraltar. Three of them resulted in the destruction or sinking of a number of Allied freighters, with a total tonnage of some 40,000 tn. Three of them were carried out by human torpedoes launched from the submarine ScirèItalian submarine Sciré (1938)
The Italian submarine Scirè was an Italian Adua-class submarine, which served during World War II in the Regia Marina. It was named after the Ethiopian region of Shire, at the time part of Italian East Africa.At the beginning of the war, Scirè was commanded by Junio Valerio Borghese, and based in...
; the other two were the work of combat swimmers.
Villa Carmela
After the attacks carried out by the Scirè, the commander of the Decima MAS realised that, given the limitations of using a submarine as a mother ship for human torpedoes in Gibraltar, it would be more feasible to mount a secret base in neutral Spain. A first step in that direction was taken when a member of the Decima, Antonio Ramognino, rented a bungalow along the coast road near Algeciras, right in front of a bay used by Allied convoys to drop anchors. The operations from Villa Carmela were carried out by combat swimmers. Because Ramognino's wife was a Spanish citizen, he had little difficulty establishing his ‘home’ there.Five merchant ships were sunk or damaged from July to September 1942 by frogmen using limpet mines. The Olterra played the role of advanced observation post for those missions.
Refitting
At the same time, another officer of the Italian special unit, Lieutenant Licio Visintini, himself a veteran of previous submarine incursions against the “Rock”, learned about the Olterra and conceived the idea of a secret mother ship for the maiali. Maiale (literally “pig”) is the Italian nickname for the human torpedoes. Under the pretext of raising the ship to sell it to a Spanish owner, a team of members of the Decima, disguised as Italian civilian workers, took control of the tanker. The ship was towed to Algeciras, where “repairs” were started. The Italian Navy personnel were helped by two civilian members of the crew. They had remained on board the half sunken oiler along with a Spanish guard for more than two years, in order to protect the rights of the Italian company which owned the Olterra. Once at docks, some of Olterras cargo holds and a boiler room were modified by Visintini men into a workshop for the assembling and maintenance of human torpedoes. An improvised observation post was also mounted on the forecastleForecastle
Forecastle refers to the upper deck of a sailing ship forward of the foremast, or the forward part of a ship with the sailors' living quarters...
to watch the Bay of Algeciras and the Allied ships at anchor there. A scene of civilian sailors working to overhaul the ship was meanwhile set up for the outsiders, in order to deceive both British and Spanish authorities. The torpedoes (in spare parts) and other equipment were smuggled into Spain by men of the Decima under the pretense of being materials for the ‘works’ on board the Olterra. Finally, a sliding hatch was open with a cutting torch six feet below the waterline. This would be the exit door of the manned torpedoes, which would launch their attacks from the flooding bilge
Bilge
The bilge is the lowest compartment on a ship where the two sides meet at the keel. The word was coined in 1513.-Bilge water:The word is sometimes also used to describe the water that collects in this compartment. Water that does not drain off the side of the deck drains down through the ship into...
, right beneath the workshop. The special unit in charge of the operations was dubbed Squadriglia Ursa Major, after the constellation of the same name
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...
.
First incursion
By the end of the autumn of 1942, the Olterra was ready for her mission. The workshop works were completed and all the supplies smuggled from Italy had reached Spain without raising any suspicion. On 6 December 1942, after taking part in Operation TorchOperation Torch
Operation Torch was the British-American invasion of French North Africa in World War II during the North African Campaign, started on 8 November 1942....
, a naval squadron consisting of the battleship HMS Nelson, the battle cruiser HMS Renown
HMS Renown (1916)
HMS Renown was the lead ship of her class of battlecruisers of the Royal Navy built during the First World War. She was originally laid down as an improved version of the s. Her construction was suspended on the outbreak of war on the grounds she would not be ready in a timely manner...
, the aircraft-carriers HMS Furious
HMS Furious (47)
HMS Furious was a modified cruiser built for the Royal Navy during the First World War. Designed to support the Baltic Project championed by the First Sea Lord of the Admiralty, Lord John Fisher, they were very lightly armoured and armed with only a few heavy guns. Furious was modified while...
and HMS Formidable and a number of escort units entered Gibraltar. Visintini planned a three manned torpedoes mission, each of them carrying 2 divers: the leading torpedo, driven by Visintini himself and Petty Officer Magro, the second by 2nd Lieutenant Cella and Sergeant Leone and the third by Midshipman Manisco and Petty Officer Varini. The targets were designated in the following order: for Visintini, Nelson, for Manisco, Formidable and for Cella, Furious.
The assault craft departed from the Olterra during the early hours of 8 December. At 2:15 AM, the first human torpedo reached the area of the boom defences. The motor launches and sentries inside the British base were quietly active and alert, conscious of the danger of a potential attack on the fleet at anchor. One of the security measures taken by the Royal Navy after the summer incursions of combat swimmers was the deployment at Gibraltar of an underwater bomb disposal unit, under the command of Lieutenant Lionel Crabb
Lionel Crabb
Lionel "Buster" Crabb OBE, GM was a British Royal Navy frogman and MI6 diver who vanished during a reconnaissance mission around a Soviet cruiser in 1956.-Early life:...
. A pattern of depth charges was dropped by the motor barges at an interval of three minutes between each one. The craft of Visintini and Magro was apparently hit by one of the charges and destroyed when they were trying to find a breach in the steel net protecting the harbour. Their bodies were recovered by the British some days later and buried at sea with full honors. The second “pig” also endured the strong response of British defences after being uncovered by a searchlight. After an endless chase by anti-submarine boats, the Italian crew decided to scuttle their craft and took shelter on board an American freighter. They discarded their swimsuits before submitting themselves to Gibraltar authorities. The last manned torpedo was caught in the middle of the general alarm across the stronghold, but managed to slip beneath the waters and fool the submarine chasers. The copilot, Leone, became missing during the pursuit and was never found; Cella, meanwhile, abandoned the craft elsewhere, thinking that he was still near Gibraltar or, in the best case, stranded close to the Spanish coast. With the idea of becoming a prisoner of war or being arrested and interned by Spanish authorities in mind, Cella surfaced, only to find that he was just a few meters away from the Olterra. His torpedo was recovered by the Italians the following day. The two divers captured by the British told their interrogators that the attack was launched by submarine, successfully deceiving Allied intelligence. Nevertheless, the first human torpedoes mission ended in failure.
Second incursion
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
also made the attacks on logistic ships a priority. In May 1943, Commander Borghese
Junio Valerio Borghese
Prince Junio Valerio Scipione Borghese was an Italian Navy commander during the regime of Benito Mussolini's National Fascist Party and was a prominent hard-line fascist politician in post-war Italy.-Early career:Junio Valerio Borghese was born in Artena, Province of Rome, Kingdom of Italy...
, of Scire, was appointed commander of the Decima. The night of the 8th was chosen for the next assault, taking advantage of the bad weather and the phase of the moon. Lieutenant Notari, along with his second, Petty Officer Ario Lazzari, was the head of another three-"pig" wave heading for Gibraltar. The second human torpedo was manned by Lieutenant Tadini and Petty Officer Mattera, and the third by Second Lieutenant Cella and Petty Officer Montalenti. In order to divert any British suspicion from the Olterra, the selected targets were merchant ships at anchor in the farthest point from Algeciras. The gale that was raging at the time hampered the mission, because the current forced them to dive around the targets before they could attach the limpet mines to the hulls. At dawn, all the Italian craft reached their mother ship safely. They had mined three vessels, the American Liberty ship
Liberty ship
Liberty ships were cargo ships built in the United States during World War II. Though British in conception, they were adapted by the U.S. as they were cheap and quick to build, and came to symbolize U.S. wartime industrial output. Based on vessels ordered by Britain to replace ships torpedoed by...
Pat Harrison (7,000 tons), and the British freighters Mahsud (7,500 tons) and Camerata (4,875 tons). When the charges exploded, the American transport was heavily damaged and became a total loss. One American sailor was killed by the blast. The Mahsud rested on the bay’s bottom with much of the ship still above the water line, while the Camerata sank outright. To mislead the British into thinking of combat swimmers instead of manned torpedoes, members of the Italian secret service scattered diving equipment along the shore. The second attempt from the Olterra had been a stunning success.
Last mission
Crash dive
A crash dive is a maneuver performed by a submarine to submerge as quickly as possible to avoid attack. Crash diving from the surface to avoid attack has been largely rendered obsolete with the advent of nuclear-powered submarines as they operate constantly submerged and are unlikely to be found on...
d to a depth of 34 meters. Then, the craft surfaced just a few feet from their intended victim. Half conscious and with no trace of his companion, Notari tried to fix the mechanical problems developed by his torpedo, but the diving mechanism was disabled. At the end, he managed to sneak out at full speed, helped by a flock of porpoises which covered his wake. Giannoli was left behind. After waiting two hours on the rudder of the ship, he shouted for help. Once Giannoli was taken on board, a motor launch carrying a member of Crabb’s diving unit was called to the scene. There was little doubt that the ship, the American Harrison Grey Otis had been mined. The warhead blew up just seconds before the British diver, Petty Officer Bell, could put his foot on the water. One sailor died and eight others were seriously injured. Like her sister ship Pat Harrison in May, the 7,700 tn Otis was declared a constructive total loss. Two other Allied ships were also rocked by explosions at the same time, about 4:00 am of 4 August. The Norwegian Thorshøvdi, of 9,900 tn was broken in two by the blast, while the British Stanridge (6,000 tons) sank in shallow water. The last mission of the Ursa Major destroyed 23,000 tn of Allied shipping.
Aftermath
Italy submitted to Allied terms on 8 September 1943. The war was over, this time for good, for the Olterra. Until then, the British in Gibraltar had no proof to link the presence of the tanker at Algeciras with the raids on their ships. In Leon GoldsworthyLeon Goldsworthy
Leon Verdi Goldsworthy GC, DSC, GM was a distinguished Australian bomb and mine specialist in the Second World War, and a recipient of the George Cross, the highest gallantry award for actions which are "not in the face of the enemy" that can be awarded to people of British or Commonwealth nations...
's words:
The Spanish authorities tried to hide the evidence, but when Crabb’s diving team boarded the Olterra after the armistice, they found spare parts from three different torpedoes. This allowed them to reassemble a full manned torpedo, named Emily. The craft was lost after six trials at open seas. Crabb met some of his former enemies after the war, including the last commander of the Ursa Major, Lieutenant Notari.
See also
- Decima MAS
- Human torpedoHuman torpedoHuman torpedoes or manned torpedoes are a type of rideable submarine used as secret naval weapons in World War II. The basic design is still in use today; they are a type of diver propulsion vehicle....
- Military history of Gibraltar during World War IIMilitary history of Gibraltar during World War IIThe military history of Gibraltar during World War II exemplifies Gibraltar's position as a British fortress since the early 18th century and as a vital factor in British military strategy, both as a foothold on the continent of Europe, and as a bastion of British sea power...