BETASOM BETASOM ( an Italian language acronym of Bordeaux Sommergibile ) was a submarine base established at Bordeaux by the Italian " Regia Marina Italiana " during World War II . From this base , Italian submarines participated in the Battle of the Atlantic from 1940 to 1943 as part of the Axis anti - shipping campaign against the Allies . Establishment . Axis naval co - operation started after the signing of the Pact of Steel in June 1939 with meetings in Friedrichshafen , Germany , and an agreement to exchange technical information . After the Italian entry into the war and the Fall of France , the Italian Navy established a submarine base at Bordeaux , which was within the German occupation zone . The Italians were allocated a sector of the Atlantic south of Lisbon to patrol . The base was opened in August 1940 , and in 1941 the captured French passenger ship was used a depot ship before being returned to the Vichy French Government in June 1942 . Admiral Angelo Parona commanded the submarines at BETASOM under the control of " Konteradmiral " ( Rear Admiral ) Karl Dönitz . Dönitz was the " Commander of the Submarines " ( " Befehlshaber der Unterseeboote " ) for the German Navy ( " Kriegsmarine " ) . About 1 , 600 men were based at BETASOM . The base could house up to thirty submarines and it had dry docks and two basins connected by locks . Shore barracks accommodated a security guard of 250 men of the San Marco Regiment . A second base was established at La Pallice in La Rochelle , France . This second base allowed submerged training which was not possible at Bordeaux . Operational detail . From June 1940 , three Italian submarines patrolled off the Canary Islands and Madeira , followed by three more off the Azores . When these patrols were completed , the six boats returned to their new base at Bordeaux . Their initial patrol area was the Northwestern Approaches and at the start they out - numbered their German allies ' submarines . Dönitz was pragmatic about the Italians , seeing them as inexperienced , but useful for reconnaissance and likely to gain expertise . Dönitz was disappointed . The Italian submarines sighted convoys but lost contact and failed to make effective reports . Even when assigned to weather reporting - critical for the war effort on both sides - they failed to do this competently . Fearing that German operations would be prejudiced , Dönitz reassigned the Italians to the southern area where they could act independently . In this way , about thirty Italian boats achieved some success , without much impact on the critical areas of the campaign . German assessments were scathing . Dönitz described the Italians as " inadequately disciplined " and " unable to remain calm in the face of the enemy " . When the British tanker " British Fame " was attacked by the " Malaspina " , " the officer of the watch and lookouts were on the bridge and the captain was dozing in a deckchair below " . It took five torpedoes to sink the tanker and , at one point , the tanker ' s gunfire forced the " Malaspina " to submerge to safety . The Italians towed the lifeboats to safety , an act worthy of praise , but one against Dönitz ' s orders and leaving the submarine open to attack for 24 hours . While the BETASOM submarines did have some value , it is clear why they did not meet the expectations of Dönitz . By 30 November 1940 , Italian submarines in the Atlantic each sank an average of 200 gross tons per day . By comparison , German U - boat s each averaged 1 , 115 gross tons per day during the same time period . But the Italian submarines sank 109 allied merchship for 593864 tons . Seven BETASOM submarines were adapted to carry critical matériel from the Far East ( " Bagnolin " , " Barbarigo " , " Cappellini " , " Finzi " , " Giuliani " , " Tazzoli " , and " Torelli " ) of which two were sunk by the Allies , two were captured in the Far East by the Germans after the September 1943 Italian Surrender and used by them and a fifth was captured in Bordeaux by the Germans , but not used . German U - boat activities . Admiral Dönitz decided during the summer of 1941 to build protective U - boat pens in Bordeaux . Construction began in September 1941 . Constructed of reinforced concrete , wide , deep , and high , with a roof above the pens thick , and thick above the rear servicing area . On 15 October 1942 , the 12th U - boat Flotilla was formed at Bordeaux by the German " Kriegsmarine " under the command of " Korvettenkapitän " Klaus Scholtz . The first U - boat to use the bunker was on 17 January 1943 . End of operations . The base was bombed by the British on several occasions . The base was indirectly attacked by Operation Josephine B in June 1941 , a raid to destroy the electricity substation that served the base . After the Italian Armistice in September 1943 the base was seized by the Germans . Some of the Italian personnel joined the Germans independently of the Italian Social Republic . During this period the Italian postage stamps on hand were overprinted to show loyalty to Mussolini ' s rump state . The last two remaining U - boat s left Bordeaux in August 1944 , three days before the Allies occupied the base on 25 August . The last remaining German naval personnel attempted to march back to Germany but were captured by U . S . forces on 11 September 1944 . List of submarines operating from BETASOM . In 1940 , all twenty - eight Italian submarines which were to be based at BETASOM initially had to sail from bases on the Mediterranean Sea and transit the Straits of Gibraltar to reach the Atlantic Ocean . All twenty - eight did this successfully without incident . In 1941 , another four Italian submarines based in Italian East Africa ( " Africa Orientale Italiana " , or AOI ) reached the base after the fall of that colony during the East African Campaign . All four had to travel around the Cape of Good Hope to get to BETASOM . Date of arrival at Bordeaux from the Mediterranean in 1940 : Transferred from the Red Sea Flotilla during the summer of 1941 : In 1941 , it was decided to return some of the boats to the Mediterranean . The " Perla " , the " Guglielmotti " , the " Brin " , the " Argo " , the " Velella " , the " Dandolo " , the " Emo " , the " Otaria " , the " Mocenigo " , and the " Veniero Glauco " made the passage but the " Glauco " was sunk by the British Royal Navy . The " Cagni " was transferred in 1942 . Post - World War II . The submarine pens have proved to be impossible to demolish due to the massive reinforced construction designed to withstand aerial bombardment . In 2010 , after conversion several years previously , approximately of the building are open to the public as a cultural centre for the performing arts , exhibitions and evening events .