As the war on terrorism continues, and along with it a heated debate over the scope of executive authority in times of national emergency, one important question deserves careful attention: how much power may Congress vest in the executive to address the crisis at hand when it chooses to take the "grave action" of suspending the privilege of the writ of habeas corpus? For example, may suspension legislation authorize the executive to arrest and detain individuals on suspicion that they might engage in future acts of terrorism? Or does suspending the privilege merely remove the courts from the governing equation without expanding the scope of executive power to arrest and detain persons of suspicion? This article seeks to provide a definitive account of what it means to suspend the privilege. Toward that end, the article explores in detail the relationship between suspension, executive power, and individual rights throughout American history along with how the suspension power fits into our larger constitutional scheme. The analysis yields the conclusion that in the narrow circumstances believed by the Framers to justify suspending the privilege--times of "Rebellion or Invasion"--a suspension offers the government some measure of latitude in its efforts to restore order and preserve its very existence. The idea is hardly new. Indeed, Blackstone articulated it long ago. As he both explained and cautioned, "[T]his experiment ought only to be tried in cases of extreme emergency; and in these the nation parts with its liberty for a while, in order to preserve it forever."