National security -- Terrorism -- Prevention. -- 8 Government policy -- 4 War on Terrorism, 2001-2009 4 Civil defense -- 3 Intelligence service -- 3 more ... Prevention -- 3 Foreign relations -- 2 Politics and government -- 2 Security measures 2 September 11 Terrorist Attacks, 2001 2 Air power -- 1 Civil defense 1 Civil rights -- 1 Defenses 1 Emergency management -- 1 Evaluation. -- 1 Foreign relations 1 Governmental investigations -- 1 Harbors -- 1 History -- 1 Information warfare -- 1 Internal security -- 1 International cooperation 1 Law and legislation -- 1 Law enforcement -- 1 Merchant marine -- 1 Military policy 1 National security 1 less ...