Abstract: Over the past half-century, discussions of constitutional war powers have focused on the scope of the President’s “inherent” power as Commander in Chief to act in the absence of congressional authorization. Professors Barron and Lederman argue that attention should now shift to the fundamental question of whether and when the President may exercise Article II war powers in contravention of congressional limitations, when the President’s authority as Commander in Chief is at its “lowest ebb.” This Article is the second part of a two-part effort to determine how the constitutional argument concerning such preclusive executive war powers is best conceived. In the companion Article, Professors Barron and Lederman described the structural forces responsible for this shift in the ground of debate and demonstrated that evidence from the Founding era does not reveal an original understanding that the Commander in Chief enjoyed preclusive authority over matters pertaining to warmaking. In this Article, they move the story forward and systematically examine how the three branches have actually considered and treated this issue from 1789 to the present day. They examine those cases in which the President has asserted or relied upon a claim of preclusive war powers. They also review the discussions of this issue that have appeared in Supreme Court opinions; in major debates on the floor of Congress; and in the leading constitutional and war powers treatises, articles, and books of the past two centuries. This historical review shows that the view embraced by most contemporary war powers scholars – namely, that our constitutional tradition has long established that the Commander in Chief enjoys some substantive powers that are preclusive of congressional control with respect to the command of forces and the conduct of campaigns – is unwarranted. In fact, Congress has been an active participant in setting the terms of battle and the conduct and composition of the armed forces and militia more generally, while the Executive (at least until recently) generally has accepted such legislative constraints as legitimate. Although history is not dispositive of the constitutional question, legislators and executive branch actors should not abandon two hundred years of historical practice too hastily, and should resist the new and troubling claim that the Executive is entitled to unfettered discretion in the conduct of war.