Introduction In military terminology@ terrorism is considered low-grade warfare. As such@ in any of the principles used to design military targets are applicable to the protective design of civilian targets subject to terrorist attack. However@ the objectives of design are different for civilian targets. For military facilities the primary objective is to maintain function after attack. 'Function' refers to essential activities such as launching a missile or maintaining communications or intelligence. For civilian facilities the primary objective is to save lives while preserving the nonmilitary character of the facility; maintaining function becomes a secondary issue. Because of this difference@ protective design principles need to be reevaluated. In this paper the fundamental principles of military facility design are used to develop a rational approach to the design of new civilian structures. These ideas are also applicable to the retrofit of existing structures. This paper is partially based on work done for the Foreign Buildings Office of the US Department of State in developing engineering guidelines for protecting US embassies abroad.