World War, 1939-1945 460 History 359 Aerial operations 155 International cooperation 130 Naval operations 124 Campaigns 118 Biography 112 Foreign relations 105 Politics and government 98 Aerial operations, American 84 National security 82 Operations research 80 Armed Forces 77 Congresses 76 Military policy 73 Aerial operations, British 67 Operating systems (Computers) 67 Thesis 62 Security, International 60 Dissertations, Academic 59 Naval operations, American 53 Terrorism 52 Juvenile literature 50 Submarine 48 Economic conditions 45 Prevention 45 World War, 1914-1918 45 United States 44 World war, 1939-1945 41 Defenses 40