This was the first in a series of war movies made by Oakmont productions in the late 1960s.
The film is loosely based on the St. Nazaire raid or Operation Chariot where an obsolete ship was filled with explosives in the bow and rammed into a German dry dock on the French coast during World War 2.
A previous film also loosely based on the same raid was The Gift Horse AKA Glory At Sea from 1952.
The miniature effects are handled by Les Bowie and are very effective with the dark night lighting certainly assisting with what would have been a relatively modest budget.
A shot of bombers on a diversionary raid seen through binoculars was lifted from Dambusters 1955.