The character and actions of the seamen are told with a crispness that is a model of editing.

Those that survive wrack up unforgettable experiences, both harrowing and heroic, though the film renders them all the more powerful for its unsentimental presentation.

The dialogue and the violence may be sanitised, but some of the ordeals faced by the story’s servicemen are scenes of powerful psychological horror.

One is grateful nowadays for a film which does not attempt to depict war as anything but a tragic and bloody experience, and it is this quality which gives the production its final power to move.