- Produced three years prior to Hitler's invasion of Poland in 1939, the movie predicts the start of WWII in 1940, only a year later than real life. It also predicts the Second World War would be fought on land, sea and air. It also predicts the use of London's Underground as a giant air raid shelter.
- Shows a helicopter several years before Sikorsky developed the first real-life model.
- The part of Theotocopulos was originally filmed with Ernest Thesiger in the role. The scenes were re-shot with Sir Cedric Hardwicke because the producers wanted a better-known actor with more "marquee value".
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