Canadian sailors defend Allied supply transport against Nazi submarines in the Atlantic Ocean during World War II

Officers on Allied ship bridge look through binoculars and telescope, searching for signs of Nazi u-boats during World War II / rear shot gun crews rush to their stations / montage sailors prepare gun, swing it into position / sailors swing torpedo tubes into position / CU torpedoes in tubes / officer watches / montage guns fire, sailors reload / from Greatest Headlines of the Century series / Note: [exact dates not known]