World War, 1939-1945 History 114 Campaigns 104 Aerial operations 45 Naval operations 27 Equipment and supplies 26 Aerial operations, British 20 Naval operations, American 14 Pictorial works 14 Tank warfare 12 Biography 10 Secret service 10 World War, 1914-1918 9 World war, 1939-1945 9 Airplanes, Military 8 Armed Forces 8 Economic aspects 8 Fighter planes 7 Juvenile literature 7 Regimental histories 7 Battles 6 History, Military 6 Personal narratives, American 6 Submarine 6 Tanks (Military science) 6 Warships 6 Aerial operations, American 5 Campaign 5 Naval operations, German 5 Personal narratives 5