Nuclear deterrence will be an essential part of U.S. security policy as long as nuclear weapons exist. It is a fact of life, rather than a Cold War artifact. Much progress can be made in reducing the centrality of nuclear weapons in U.S. foreign policy and in drawing closer to the ultimate goal of disarmament within the framework of a policy of nuclear deterrence. Tannenwald champions disarmament as an "idea whose time has come," but in order for disarmament not to threaten U.S. security dramatically, it must be 100 percent effective—and verifiably so. Because of the extreme military advantage that nuclear weapons grant their possessors, no nuclear weapons state can afford the relative loss of power that would come from disarming while another state did not. Thus, total nuclear disarmament is a difficult, if not impossible, proposition. Nuclear weapons states need to maintain their arsenals, which means they must maintain a doctrine of deterrence.