 The St Nazaire Raid or Operation Chariot was a successful British amphibious attack on the heavily defended Normandie dry dock at St Nazaire in German @-@ occupied France during the Second World War . The operation was undertaken by the Royal Navy and British Commandos under the auspices of Combined Operations Headquarters on 28 March 1942 . St Nazaire was targeted because the loss of its dry dock would force any large German warship in need of repairs , such as the Tirpitz , to return to home waters via either the English Channel or the <unk> gap , both of which were heavily defended by British units including the Royal Navy 's Home Fleet , rather than having a haven available on the Atlantic coast . 
