At the time this film was released in 1940, World War II had already begun in Europe, but the Soviet Union still had a non-aggression pact with Nazi Germany. In the film, Mac is able to fool a character by pretending to hear news that Germany has broken the pact and launched an invasion of the USSR. That's exactly what happened the very next year when Germany launched Operation Barbarossa in summer 1941.
The fleeing of the inept Romanian army in the wake of the single Soviet tank commandeered by Mac (Clark Gable) presaged the Soviet army's smashing of the Romanian Third Army in Operation Uranus in November 1942, leading to the first major Soviet victory of the war, the Battle of Stalingrad.
Paul Morrissey (director of many Andy Warhol films) once acknowledged that this was his favorite movie.
At the marriage license bureau, Theodore tells Mac that she had been married twice before. At the time the film was released in December 1940, Hedy Lamarr had been divorced from her second husband, Gene Markey, for about two months.