World War I espionage

His silent film 'Spies' (1928) is a masterpiece of espionage cinema that explores WWI-era spy networks and double agents with expressionistic intensity.

Though primarily known for later work, his early films like 'The Lodger' (1927) and 'Blackmail' (1929) drew heavily on WWI espionage anxieties and suspicion.

His film 'Leaves from Satan's Book' (1921) and other works engage with WWI themes including espionage, betrayal, and the moral ambiguities of wartime deception.