Espionage History 113 Spies 76 Intelligence service 68 Secret service 31 Cold War 22 World War, 1939-1945 21 more ... Foreign relations 19 Subversive activities 16 Politics and government 14 Espionage, Soviet 13 Military intelligence 13 Communism 8 Prevention 7 Terrorism 7 Electronic surveillance 6 Moral and ethical aspects 6 National security 6 World War, 1914-1918 6 Officials and employees 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 Assassins 3 Confidential communications 3 Espionage, American 3 less ...