The raid by the Royal Navy and British Commandos was overseen by Combined Operations Headquarters. Their task was to disable the only dry dock on the Atlantic seaboard that was big enough to accommodate the terrifying German battleship Tirpitz. This was vital to British attempts to weaken the German presence in the Atlantic. If the St Nazaire facility could be put out of action, the Germans would have to send Tirpitz home for any repairs and would ultimately keep the dangerous ship out of the Atlantic.
265 commandos and 346 Royal Navy personnel arrived at the French docks in a convoy led by the old British destroyer HMS Campbeltown in the early hours of 28 March. The convoy was spotted before reaching the enormous gates of the dry dock but, despite of intense fire from the German batteries on the shore, Campeltown ploughed into the dock gates at 1.34am. Commandos surged ashore to destroy key dock facilities with explosives while assault teams tried to draw away German defenders. Meanwhile, time fuses attached to explosives hidden in the bow of Campbeltown were set.
With almost all the British evacuation ships destroyed or unable to reach the docks, it became clear that the Commandos left on shore would be unable to leave by sea. They consequently fought on until they ran out of ammunition, after which all but five were taken prisoner. At around noon the explosives inside Campbeltown detonated, destroying the dry dock.
Only 228 men returned to England. 169 had been killed and 205 became prisoners of war, but the raid itself was a success as the dock remained inoperative for the rest of the war.