In 1944, a squadron of Mosquito fighter-bombers is ordered to attack a German rocket fuel factory, which is located at the far end of a heavily-defended fjord in occupied Norway.
In the film, "633" is consistently pronounced as "six three three," not as "six hundred and thirty-three."
Tropes in the book and film:
- Airstrike Impossible: One of the the two Trope Makers along with The Dam Busters (which together inspired the Trope Codifier, A New Hope). The German factory is at the far end of a narrow fjord, with anti-aircraft guns all along it. It is in a cave under overhanging rock. The rock protects the factory from being bombed from above. However, if the overhang can be bombed at its base, then it will break off the mountain wall and bury the factory.
- Anyone Can Die: People start dying before the mission even starts. For variety, one is blinded.
- Bittersweet Ending: The mission is successful, but at great cost: all of the planes are lost, and the crews who do not die will become prisoners. The Norwegian resistance cell is discovered by the Germans, and wiped out.
- Cold Equation: A Norwegian resistance member who knows about the operation is captured by the Germans. Roy Grant has to bomb Gestapo HQ in Bergen before they can make him talk, and blow the whole mission.
- Eagle Squadron: The lead pilot is Roy Grant, an American. He tells a Norwegian refugee that before the war he was a barnstormer, and he signed up because he needed something to do after the barnstorming company folded. The film is silent on why he stayed on with the RAF after Pearl Harbor.
- Equal-Opportunity Evil: The Gestapo agent who tortures Bergman is a woman.
- "Everybody Dies" Ending: The only members of 633 Squadron and the Norwegian resistance cell still alive or uncaptured are staff officers and ground crew that never left England.
- The Film of the Book: The more famous film is based on a novel, which was loosely based on a number of real RAF strike missions, particularly the air raids against the Bismarck-class battleship Tirpitz.
- La Résistance: The mission is planned in cooperation with a cell of Norwegian resistance fighters.
- We Have Reserves: After the mission, one of the ground officers asks the base commander "All that sacrifice, what does it add up to?" The commander replies "A successful mission."
- Weapons Understudies: While the eight De Havilland Mosquitoes used in the film are the genuine article, no German aircraft of the right types were available. The Bf 109s in the film are portrayed by Nord Pingouins, a French copy of the Bf 108 Taifun (which was frequently used as a stand-in during the period).
