World War, 1939-1945 History 427 Campaigns 421 Biography 137 Aerial operations 93 Naval operations 78 Aerial operations, British 54 Regimental histories 49 Secret service 48 Tank warfare 47 Naval operations, American 41 Germany 40 Personal narratives, American 40 Personal narratives, British 40 Equipment and supplies 39 Personal narratives 37 History, Military 34 Aerial operations, American 32 Submarine 32 Foreign relations 31 Juvenile literature 30 World War, 1914-1918 30 Pictorial works 29 Causes 28 Great Britain 26 Diplomatic history 24 Military intelligence 24 United States 24 World war, 1939-1945 24 Naval operations, British 23