As soon as the first cells were built, the base became the home port of the 12. Unterseebootsflottille. This flotilla was responsible for long-haul missions, including those to the Indian Ocean and connections with Japan1.
The port of Bordeaux and its outbuildings (Le Verdon, Ambès, Bassens, Pauillac) were also home to a flotilla of some twenty patrol boats, fifteen minesweepers and a number of destroyers tasked with providing protection for the departure and arrival of submarines.
May 17, 1943 saw a major American air raid. Information from the Resistance had alerted the Allies to a heavy concentration of submarines4. But the bombing raid, carried out at 22,000 feet, was imprecise and had little effect on the base. One of the dock gates was destroyed and five submarines ran aground4. But the damage to civilians was considerable, with over 200 buildings hit, 184 Bordeaux residents killed and 249 wounded4. Between January and August 1944, more than 13 Anglo-American raids took place on the Mérignac submarine base and airport, but without much success4.
On August 28, 1944, Bordeaux and the port were evacuated by the Germans. Source wikipedia