Secret service World War, 1939-1945 History 57 Spies 28 Underground movements 14 Military intelligence 13 Intelligence service 10 more ... Campaigns 8 Espionage, German 8 War 8 Espionage 7 Intelligence officers 7 Cryptography 6 Espionage, British 6 Holocaust, Jewish (1939-1945) 6 Anti-Nazi movement 5 Foreign relations 5 Electronic intelligence 4 Espionage, Soviet 4 Aerial operations, American 3 Aerial operations, British 3 Air pilots, Military 3 Cold War 3 Collaborationists 3 Escapes 3 Flight crews 3 International relations 3 Special operations (Military science) 3 War criminals 3 American 2 less ...