World War, 1939-1945 1,584 History 1,042 World politics 700 Campaigns 612 Foreign relations 374 Biography 294 World War, 1914-1918 244 Juvenile literature 216 International relations 215 World war, 1939-1945 175 Politics and government 162 Aerial operations 133 Military policy 119 World War 112 Naval operations 107 United States 101 Terrorism 94 Armed Forces 83 National security 81 Pictorial works 80 Islam 79 Economic conditions 78 Airplanes, Military 76 Regimental histories 75 Secret service 71 Leadership 69 War 67 Security, International 66 Aerial operations, British 64 Military art and science 64