The ship was significantly modernised in the interwar period, and when she was on active duty, conducted normal peacetime cruises and training manoevres in the Mediterranean and the Atlantic Ocean. After World War II broke out in September 1939, "Bretagne" escorted troop convoys and was briefly deployed to the Atlantic in search of German blockade runners and commerce raiders. Germany invaded France on 10 May 1940 and the French surrendered only six weeks later, at which time the battleship was stationed in Mers-el-Kébir, French Algeria. Fearful that the Germans would seize the French Navy, the British attacked the ships there on 3 July 1940 after the French refused to surrender or demilitarise the fleet; "Bretagne" was hit four times and exploded, killing the majority of her crew. Her wreck was salvaged in 1952 and broken up for scrap.