Defenses 3 Terrorism -- Civil defense -- 2 National security -- 2 Prevention -- 2 Asymmetric warfare -- 1 Civil defense 1 more ... Emergency management -- 1 Government policy -- 1 Harbors -- 1 Merchant marine -- 1 Military policy 1 National security 1 Politics and government -- 1 Prevention 1 Security measures 1 Security measures -- 1 War on Terrorism, 2001-2009 1 Weapons of mass destruction 1 less ...