Espionage History 106 Spies 70 Intelligence service 67 Secret service 29 Cold War 20 Foreign relations 19 more ... World War, 1939-1945 19 Subversive activities 16 Espionage, Soviet 13 Military intelligence 13 Politics and government 13 Communism 8 Prevention 7 Terrorism 7 Electronic surveillance 6 Moral and ethical aspects 6 National security 5 Officials and employees 5 World War, 1914-1918 5 Equipment and supplies 4 Law and legislation 4 Political aspects 4 Presidents 4 World politics 4 Anti-communist movements 3 Arab-Israeli conflict 3 Confidential communications 3 Espionage, American 3 Fedayeen 3 less ...