History World War, 1939-1945 Campaigns 27 Equipment and supplies 14 Aerial operations, British 12 Naval operations 11 Aerial operations 5 Airplanes, Military 5 Armed Forces 5 World War, 1914-1918 5 Campaign 4 Equipment 4 Aerial operations, American 3 Germany 3 Military intelligence 3 Military weapons 3 Pictorial works 3 Regimental histories 3 Secret service 3 Underground movements 3 Warships 3 Design and construction 2 Firearms 2 France 2 Great Britain. Royal Air Force 2 Insignia 2 Juvenile literature 2 Military art and science 2 Military uniforms 2 Naval operations, German 2