Submarine I-57 Will Not Surrender (1959)

Original title: 潜水艦イ-57降伏せず

In World War II, the commanding officer of a sub, against his will takes on board two Western diplomats, to take them to the Canaries and arrange an armistice. When they get there, peace has been declared, but the sub's crew don't know as their radio has failed. They send their passengers ashore and go out to face a final battle...