Until 1950 it had long been established and well settled that the Constitution vests in Congress the sole and exclusive authority to initiate total as well as limited war. But at the midcentury mark, President Harry Truman asserted a unilateral executive warmaking power, and claimed authorization from the United Nations, to justify his decision to introduce U.S. troops into the Korean War without congressional authorization. Truman's decision in June 1950 to intervene in South Korea in order to counter the communist North Korean invasion commenced what was to become one of the bloodiest wars in America history. The president claimed that he acted in response to a UN Security Council call for military action. In fact, Truman had committed U.S. forces before the Security Council issued its request. Several senators and representatives attacked Truman's unilateral act on the floor of Congress as a violation of the Constitution. They point out that the UN Charter carried no specific obligation to go to war in support of its decisions any more than a treaty obligation alone could commit the United States to war without a decision to that end by both houses of Congress. Thus, Robert Taft of Ohio, in an embittered speech on the Senate floor, charged that President Truman had "usurped power and violated the Constitution" by his Korean intervention. Despite constitutional doubts expressed by Taft and several other senators, Congress regularly appropriated ample funds to support the war. In reality, it had little choice in the matter, unless it wished to see an American army far from home overwhelmed in the field.
In 1951, while the Korean War was still in progress, Truman announced that he was sending four army divisions to Germany in support of the new U.S. obligation to defend the Continent, in accordance with the North Atlantic Treaty and the Lisbon and Ottawa agreements. It was obvious that a large-scale American army on the Elbe River opposite Soviet-occupied East Germany constituted a heavy American commitment to go to war in the event of a Soviet invasion of western Europe, regardless of any constitutional limitation upon the war power. Indeed, the American divisions were commonly described as a "trip wire" for the very purpose of committing the United States to war should such an invasion occur.
Truman denied that he need congressional authorization before deploying the troops in Europe, and his decision triggered the so-called "great debate" on the constitutionality of his action. Several senators, among them Paul Douglas and Thomas Connelly, argued that the president has the power under the Constitution to move troops overseas, both in pursuance of treaty obligations and by virtue of his constitutional powers as commander in chief of the armed forces. In contrast, Taft and John Bricker criticized the president's action as grossly unconstitutional.
The outcome of the debate was a substantial victory for the president. The Senate adopted a weak resolution expressing its "approval" of the president's action, but declaring it to be "the sense of the Senate" that in the future the president ought to obtain the approval of Congress prior to the assignment of troops abroad, "in the interests of sound constitutional processes and of national unity." The acquiescence of Congress in the fact of Truman's usurpation of power inaugurated a new theme in matters of war and peace.
Since then a steady pattern of presidential warmaking has developed: Lyndon Johnson and Richard Nixon in Vietnam, Gerald Ford in Cambodia, Ronald Reagan in Lebanon, Grenada, and Libya, George H. W. Bush in Panama, and William Jefferson Clinton in Somalia, Iraq, Afghanistan, Sudan, and Bosnia, all without congressional authorization.
Following Iraq's invasion of Kuwait on 2 August 1990 under the leadership of Saddam Hussein, President George H. W. Bush began deploying U.S. troops to Saudi Arabia and other sites in the Middle East. By November, Bush had doubled the size of the deployment and established the capacity to wage war. Bush did not seek authorization from Congress, but persuaded the United Nations Security Council to authorize the use of military force, which it did on 29 November. Bush never sought authority (only support) from Congress, but on 12 January 1991 Congress authorized military action against Iraq. The approval, however, bore the appearance of a rubber stamp in the face of a presidential fait accompli, backed by a bloc of 439,000 U.S. troops that Bush had amassed in the region. There is surely nothing in the constitutional grant of authority to the president that justifies the deployment of troops, but in the postwar era, presidents frequently have deployed troops into hostilities or into situations in which hostilities were imminent, in numbers large and small and for durations long and short, a practice that has served to preempt the congressional power to decide on matters of war and peace.
Congressional acquiescence in the presidential usurpation of its authority to deploy troops has become a central factor in the demise of legislative control of the war power which, Madison stated, includes the power "to commence, continue and conclude war." President Bush's claim of UN authority—like Truman's in Korea or Clinton's invocation of authority from NATO to order air strikes against Yugoslavia on 24 March 1999— lacks credibility. These mutual security treaties provided that they would be carried out by the United States in accordance with its "constitutional processes," which vests in Congress the sole power to decide for war. The fact that treaties are the supreme law of the land does not imply that a mutual security treaty can amend the Constitution. In Geofroy v. Riggs (1890), the Court stated that the treaty-making power does not "authorize what the Constitution forbids, or [effect] a change in the character of government." Thus, the president and the Senate may not, through the exercise of the treaty power, deprive the House of Representative of its constitutional role as a joint partner in the warmaking power with the Senate.
Presidents have asserted a variety of arguments in defense of their unilateral military actions. Invocation of the commander in chief clause has become a commonplace. As Justice Robert H. Jackson observed in the Steel Seizure Case (1952), the clause has been adduced for the "power to do anything, anywhere, that can be done with an army or navy." Yet neither the history of the clause nor the debates in the Constitutional Convention afford any evidence to support this presidential claim. Moreover, no court has ever cited it as a source of independent warmaking authority for the president.
Twentieth-century presidents including Truman, Nixon, and Clinton also have advanced the executive power clause as authorization for presidential warmaking. Article 2, Section 1, of the Constitution provides: "The executive Power shall be vested in a President of the United States of America." As we have seen, the claim that the executive power clause includes authority to initiate hostilities was considered and rejected in the Constitutional Convention. For the Framers, the phrase "executive power" was limited, as James Wilson said, to "executing the laws, and appointing offices." No delegate to the convention sought to ascribe to the president a more capacious understanding of "executive power" than that articulated by Wilson.
Advocates of a unilateral executive warmaking power also have invoked the "Lockean prerogative," or the doctrine of necessity, as a source of inherent presidential power. Drawing on John Locke's defense of the right of an executive to act for the common good, even if it requires breaking the law, defenders have adduced a similar claim for the president. But there is no evidence whatever that the Framers intended to incorporate the Lockean prerogative in the Constitution. The lack of a textual statement to that effect renders such an intent indispensable to the presidential claim of a constitutional power. In fact, the evidence runs in the other direction. Fears of executive power led the Framers to enumerate the president's power and to "define and confine" the scope of his authority. An undefined reservoir of discretionary power in the form of Locke's prerogative would have unraveled the carefully crafted design of Article 2 and repudiated the Framers' stated aim of corralling executive power.
Presidents have also asserted a presidential warmaking authority on the basis of his role as the "sole organ" of American foreign policy. In Curtiss-Wright, Justice Sutherland stated that the authority in foreign affairs was essentially an executive power, which he explained "as the very delicate, plenary and exclusive power of the President as the sole organ of the federal government in the field of international relations—a power which does not require as a basis for its exercise, an act of Congress." Sutherland appropriated the term "sole organ" from a speech delivered by then Representative John Marshall in 1800 on the floor of the House of Representatives. Marshall noted: "The President is the sole organ of the nation in its external relations…. Of consequence, the demand of a foreign nation can only be made on him." At no point in his speech did Marshall argue that the president's exclusive authority to communicate with a foreign nation included a power to formulate or develop policy. All Marshall had in mind was the president's role as the sole organ of communication with other governments, a rather unremarkable point, at that, since officials had acknowledged since the founding that the president was the "sole" channel of communication with foreign nations. Thus it was Sutherland who infused a purely communicative role with a substantive policymaking function and thereby manufactured a great power out of the Marshallian "sole organ" doctrine. Of course, the sole organ doctrine completely undermines the Framers' design for cooperation in foreign affairs. And, given the allocation of foreign relations power to both Congress and the president, the claim is by definition indefensible.
Extollers of presidential control of the war power also have fashioned the argument that executive warmaking, if repeated often enough, acquires legal validity. This is the contention that history has legitimated the practice of presidential warmaking. The argument rests on the premise that the president frequently has exercised the war power without congressional authorization. The actual number of these episodes varies among the several compilations, but defenders usually list between one and two hundred unilateral acts, each of which constitutes a legitimizing precedent for future executive wars. In detail and in conception the argument is flawed. In the first place, the lists are inaccurately complied. An error common to the lists—the claim that President John Adams initiated unilateral executive warmaking in 1798 in an "undeclared war" with France—is altogether false. The fact is that Adams took absolutely no independent action. Congress passed some two dozen statutes that amounted, so the Supreme Court said, to a declaration of "imperfect war," and Adams complied with those statutes. Moreover, many of the episodes involved initiation of hostilities by a military commander, not by authorization from the president. If practice establishes law, then the inescapable conclusion is that every commander of every military unit has the power to initiate war. What is perhaps most revealing about presidential understanding of the constitutional locus of the war power is that in the one or two dozen instances in which presidents personally have made the decision unconstitutionally to initiate acts of war, they have not purported to rely on their authority as commander in chief or chief executive. Rather, in those cases the presidents have made false claims of authorization, either by statute or by treaty or by international law. It cannot be maintained that constitutional power, in this case the war power, can be acquired through practice. Writing for a unanimous Court in Inland Waterway Corp. v. Young (1940), Justice Frankfurter echoed a centuries-old principle of Anglo-American jurisprudence when he wrote: "Illegality cannot attain legitimacy through practice." If the president could acquire power through usurpation he might aggrandize all governmental power. Neither Congress nor the judiciary could lawfully restrain the exercise of the president's accumulated constitutional powers. This practice would scuttle U.S. constitutional jurisprudence. Thus, the most recent act of usurpation stands no better than the first.
In the post–World War II period presidential usurpation of the war power has been indulged by congressional acquiescence, for policy as well as political reasons. But it is unwarranted to conclude that presidential aggrandizement, indulged by congressional passivity, attains a legal status. Congress cannot divest itself of those powers conferred upon it by the Constitution, a necessary predicate of the separation of powers doctrine. Neither congressional abdication nor acquiescence can accomplish a transfer of power to the executive. As the Court held in Federal Trade Commission v. Morton Salt Company (1950), harking back to an old axiom of English law, once powers are "granted, they are not lost by being allowed to lie dormant, any more than non-existent powers can be prescripted by an unchallenged exercise."
In a somewhat anemic effort to reassert its control of the war power, Congress passed, within the context of the debate surrounding the Vietnam War, the War Powers Resolution of 1973, over President Nixon's veto. The statute sought to curb presidential warmaking and to require "the collective judgment" of the president and Congress before U.S. troops could be committed to hostilities. In the absence of a declaration of war or authorization by statute, the statute required the president to consult Congress before introducing U.S. forces into hostilities "in every possible instance," to report to Congress when he has done so, and to terminate the involvement after sixty days unless Congress authorized an extension. The resolution was criticized as an ill-conceived and poorly drafted piece of legislation. Its chief defect from a constitutional standpoint lay in the fact that it represented an unconstitutional delegation of the war power. In its grant to the president of the authority to choose an "enemy" of the United States, and to initiate hostilities against the nation, it not only repudiated the statutory aim of ensuring "collective judgment" of both branches, but it also vested in the president power that is denied to him by the Constitution. Virtually every American president who took office after its passage found ways to circumvent the resolution. Unconstitutional, ill-conceived, and ineffective, the resolution amounted to what Arthur Schlesinger Jr. described as a "toy handcuff," and by the early twenty-first century there was wide agreement that it ought to be repealed.