World War, 1939-1945 History 40 World War, 1914-1918 18 Equipment and supplies 16 Campaigns 15 Biography 14 Foreign relations 10 Aerial operations 7 Aerial operations, British 7 Naval operations 7 Aerial operations, American 6 Airplanes, Military 6 Causes 6 Fighter planes 6 Secret service 6 Diplomatic history 5 Military history, Modern 5 Personal narratives, American 5 Tank warfare 5 War 5 Armed Forces 4 Army 4 Commando operations 4 Generals 4 Germany 4 Great Britain 4 History, Military 4 Naval operations, British 4 Pictorial works 4 War and society 4