During the Battle of the Atlantic, after sinking a merchant ship from an Allied convoy, German U-boat "U-571" has her engines badly damaged by depth charges from a British destroyer. "U-571's" skipper "Kapitänleutnant" Günther Wassner makes a distress call that is intercepted by American intelligence. The US Navy has its submarine "S-33" modified to resemble a German resupply U-boat, to try to steal the Enigma machine coding device and sink the "U-571". Before the crew of "S-33" receives its assignment, the submarine's executive officer Lieutenant Tyler is unhappy about a recommendation for command of his own submarine being blocked by his commanding officer, Lieutenant Commander Dahlgren.