North Atlantic Treaty Organization 35 Defenses 26 History 25 Military policy 24 Armed Forces 21 Security, International 17 Foreign relations 16 National security 15 Treaties 13 World politics 10 North Atlantic Treaty Organization (NATO) 8 Congresses 6 Europe 6 Military relations 6 Politics and government 6 North Atlantic treaty organization 5 Nuclear nonproliferation 5 Strategic aspects 5 20th century 4 Air forces 4 Collections 4 International relations 4 Islam 4 Membership 4 Strategy 4 Bombing, Aerial 3 International security 3 Nuclear energy 3 Nuclear warfare 3 Treaty on the non-proliferation of nuclear weapons 3