Factual error: When William Holden visits the Special Operations HQ for the first time a black vehicle is seen pulling in to the complex. The car is a 1948 Dodge or other Chrysler product which had not yet been manufactured.
Factual error: When the UBoat changes course, Andrews, operating the radar repeater, is immediately able to provide the bridge with the target's new course and speed. This would be impossible without extensive calculations and at least range and bearing plots once the target has steadied up on the new course, either figured on the scope screen or on a maneuvering board. One must remember that both vessels' courses and speeds must be taken into account when making computations, and the relative direction of a target's travel most often is not its true course.
Factual error: As the movie opens, the submarine is dispatching frogmen to acquire Japanese mines that are sonar-proof. The problem with this is that in order to locate mines by sonar, either the mines must make noises to be picked up by passive hydrophones, or the submarine has to start pinging with active sonar. Doing this makes the submarine vulnerable to any enemy listening in. I can't imagine a submarine venturing into a mined strait, announcing to one and all, "Here I am"..
Factual error: Montana introduces himself as Sergeant First Class Montana, but his helmet and sleeve insignia shows the rank of Staff Sergeant.
Factual error: Sgt. Brennan and the Base Commander are riding in a staff car. They get out to see new runway construction, and when they get back in the car, Sgt. Brennan gets in first, followed by the Base Commander. Sgt. Brennan is on the right in the rear seat. According to proper protocol, the junior person sits to the left of the senior person. He should have been to the left of the CO.