Terrorism -- 4 United States National security -- 3 Prevention 3 Security Management 2 Civil security -- 1 Economic development 1 more ... Foreign relations 1 Foreign relations -- 1 Homeland security 1 Infrastructure -- 1 International relations 1 Military policy 1 Safety measures 1 Security measures 1 September 11 Terrorist Attacks, 2001 1 Transportation -- 1 War on terrorism, 2001- 1 less ...