National security -- Terrorism -- Prevention -- 18 Prevention. -- 11 Government policy -- 9 Civil defense -- 5 Congresses 5 more ... Foreign relations -- 5 International cooperation 5 Prevention 5 Civil rights -- 4 Congresses -- 4 Emergency management -- 4 Foreign relations 4 History -- 4 Security measures 4 War on Terrorism, 2001-2009 4 Intelligence service -- 3 Military policy 3 Pirates -- 3 Politics and government -- 3 September 11 Terrorist Attacks, 2001 3 Terrorists -- 3 United States 3 War on terrorism, 2001- 3 Defenses 2 Government policy 2 International relations 2 Law and legislation 2 Law enforcement -- 2 less ...