National security -- Terrorism -- Prevention -- 12 Prevention. -- 11 Government policy -- 5 Prevention 5 Congresses 4 more ... Security measures 4 War on Terrorism, 2001-2009 4 Civil defense -- 3 Congresses -- 3 Emergency management -- 3 Foreign relations 3 Foreign relations -- 3 Intelligence service -- 3 International cooperation 3 Military policy 3 September 11 Terrorist Attacks, 2001 3 Terrorists -- 3 United States 3 Government policy 2 Law and legislation 2 Merchant marine -- 2 Pirates -- 2 Political violence -- 2 Politics and government -- 2 Security Management 2 Terrorism 2 Air power -- 1 Civil defense 1 less ...