Factual error: Miller rigs his booby trap by attaching the wires from the bomb to a pole down which a metal runner slides, so that when the runner touches the wires it completes the circuit and detonates the bomb. The trouble is, the pole is made of steel, and steel is very conductive indeed. Miller attaches the exposed end of the wire to the pole without any insulation or gap. The circuit will actually be completed when Miller attaches the battery, and he and his booby trap will be blown sky high.
Plot hole: Maria describes in lurid detail how Anna was arrested by the Germans and tortured by being severely whipped, leaving her with gruesome scars all over her back. She also says that Anna hasn't spoken a word to anyone since she escaped from captivity. How, then, does Maria (or anyone else) know about the scars? Nobody saw them (they don't exist) and Anna obviously didn't tell anyone about them.
Trivia: At the very end of the film when Gregory Peck and David Niven are standing on the deck of the warship watching the explosions, you can see a very distinctive injury on Niven's upper lip. During the filming of the sequence where the commandos climb the cliffs he was slammed into the rock face by the water dumped on them to simulate the waves breaking over them. The resulting infection put him in hospital. He complains about the indifference of the film's producers in his book "The Moon's A Balloon."PEDAUNT
Corporal Miller: Sir, I've inspected this boat, and I think you ought to know that I can't swim.
Squadron Leader Howard Barnsby raaf: First, you've got that bloody old fortress on top of that bloody cliff. Then you've got the bloody cliff overhang. You can't even see the bloody cave, let alone the bloody guns. And anyway, we haven't got a bloody bomb big enough to smash that bloody rock. And that's the bloody truth, sir.