49th Parallel is a 1941 British war drama film. It was the third film made by the British filmmaking team of Michael Powell and Emeric Pressburger. It was released in the United States as The Invaders. The British Ministry of Information approached Michael Powell to make a propaganda film for them, suggesting he make "a film about mine-sweeping". Instead, Powell decided to make a film to help sway opinion in the then-neutral United States. Said Powell, "I hoped it might scare the pants off the Americans" and thus bring them into the war. Screenwriter Emeric Pressburger remarked, "Goebbels considered himself an expert on propaganda, but I thought I'd show him a thing or two". Powell persuaded the British and Canadian governments and started location filming in 1940, but by the time the film appeared, in March 1942, the United States, which had been trying to stay out of the war in Europe, had been drawn into taking sides against Germany after being attacked three months earlier.

Esmond Penington Knight was an English actor. He had a successful stage and film career before World War II. For much of his later career Knight was half-blind. He had been badly wounded in 1941 while on active service on board HMS Prince of Wales when she fought the Bismarck at the Battle of the Denmark Strait, and remained totally blind for two years, though he later regained some sight in his right eye.