World War, 1939-1945 1,583 Campaigns 612 History 605 World War, 1914-1918 244 Biography 208 World war, 1939-1945 175 Aerial operations 132 World War 112 Naval operations 106 Regimental histories 75 Secret service 66 Aerial operations, British 64 Personal narratives 59 Tank warfare 58 Germany 52 Equipment and supplies 51 Personal narratives, British 51 History, Military 49 Juvenile literature 49 Submarine 49 Causes 47 Naval operations, American 45 Foreign relations 44 Personal narratives, American 43 Great Britain 41 Pictorial works 38 Soldiers 38 United States 38 Aerial operations, American 37 Diplomatic history 36