World War, 1939-1945 Campaigns 231 History 211 Aerial operations 72 Biography 69 Naval operations 50 Equipment and supplies 30 Secret service 28 Aerial operations, British 27 Tank warfare 27 Naval operations, American 26 Personal narratives 23 Personal narratives, American 23 Germany 21 Personal narratives, British 21 Regimental histories 19 Juvenile literature 18 Pictorial works 17 Submarine 17 History, Military 16 Aerial operations, American 14 Armed Forces 14 Great Britain 14 Military intelligence 14 Airplanes, Military 13 Atrocities 13 Causes 13 Foreign relations 13 Naval operations, British 13 United States 13