National security -- 15 Terrorism -- 11 Prevention. -- 7 War on Terrorism, 2001-2009 5 Civil defense -- 3 Government policy -- 3 Intelligence service -- 3 more ... Politics and government -- 3 Defenses 2 Foreign relations -- 2 Military policy 2 Security measures 2 September 11 Terrorist Attacks, 2001 2 Air power -- 1 Civil defense 1 Economic aspects -- 1 Emergency management -- 1 Energy policy -- 1 Evaluation. -- 1 Foreign relations 1 Government spending policy -- 1 Governmental investigations -- 1 Harbors -- 1 Information warfare -- 1 Internal security -- 1 Law enforcement -- 1 Merchant marine -- 1 National security 1 Nuclear weapons information -- 1 Petroleum industry and trade -- 1 less ...