World War, 1939-1945 Campaigns 45 History 45 Aerial operations 21 Naval operations 15 Equipment and supplies 14 Secret service 8 Aerial operations, British 7 History, Military 6 World war, 1939-1945 6 Airplanes, Military 5 Military intelligence 4 Personal narratives, American 4 Pictorial works 4 Tank warfare 4 Battles 3 Economic aspects 3 Fighter planes 3 Foreign relations 3 Personal narratives, British 3 Submarine 3 Warships 3 World War, 1914-1918 3 Aerial operations, American 2 Armed Forces 2 Armoured vehicles, Military 2 Army 2 Biography 2 Causes 2 Chronology 2