The film depicts an account of Allied Combined Operations Headquarters commandos executing a daring raid on the German-occupied French coast during the Second World War.

[citation needed][4] Canadian Commando Major Jamie Wilson plans an audacious Combined Operations raid on the Axis held French port of Le Clare; if destroyed, the Germans would be stripped of the only dry dock capable of servicing their large battleships.

After an attack by a night fighter delays their return to base course, Wilson is surprised to learn that Franklin had suggested they minesweep the area in the weeks before the mission so the Germans believe it to be just routine.

Meanwhile, a German party, led by von Horst's subordinate, Captain Erich Strasser, boards the minesweeper and heads for the smashed bridge where Wilson, barely alive, notices that the detonating circuit is broken.

Encouraged by the worldwide success of 633 Squadron (1964), producer Walter Mirisch proposed a series of British-made films with a military theme having major American stars in the lead that would comply with the Eady Levy requirements and cost no more than US$1 million.

Each of the films was approximately 90 minutes long, making them suitable for half of a double feature and had a Hollywood star leading the cast.