World War, 1939-1945 58 History 56 Campaigns 41 Foreign relations 36 Military campaigns 31 Politics and government 31 Economic conditions 22 more ... Diplomatic relations 14 International relations 14 Armed Forces 10 Imperialism 10 Social conditions 10 Economic policy 9 Social aspects 9 Aerial operations, American 8 Foreign economic relations 8 International economic relations 8 Relations 8 American 7 History, Military 7 Discovery and exploration 6 History and criticism 6 In literature 6 Military relations 6 National security 6 Naval operations, American 6 Security, International 6 Strategic aspects 6 Causes 5 Discoveries in geography 5 less ...