The threat of terrorism, which created the vogue for a national ‘‘homeland security’’ infrastructure, must be understood in a strategic context. Terrorist attacks have direct costs, but they also seek self-injurious overreaction, such as the waste of blood and treasure on the part of the victim state; recruitment and sympathy gains when the victim state misdirects a violent response; and the weakening of the political order in the society attacked so that it is induced to act wrongly. When it does so, it cedes the moral and ideological high ground, making terrorists groups look relatively more legitimate.

Policymakers should use risk management to prioritize security efforts, and they should avoid holding out the promise of perfect security, as there is no such thing. Civil liberties must be fully protected, and doing so is consistent with proportionate and well-focused domestic security efforts.