From September 1940 was La Pallice the alternative base for the Italian Betasom submarines (the main base of operations being Bordeaux). The 3rd Flotilla took over the base on October 27, 1941.
In April 1941 the German Command decided to build also a bunker in La Pallice. The first two pens were finished in October 1941. The U-boat bunker was 195 m wide, 165 m long and 19m high. The first U-boat in the bunker was U-82 on November 19, 1941. Then followed U-332 (16th December) and U-432 (24th December).