Under Ten Flags

Under Ten Flags is a fact-based British maritime epic set during World War II. Allied ships are being victimized by a German surface raider, which sails under friendly flags until moving in for the kill. The Germans seem the cleverest and most resourceful of all the combatants; at times, one hopes that they'll get away with their high-seas perfidy--especially since the captain is played by charismatic American actor Van Heflin. (Answers.com)