Welcome back to our Learning Journey on the evolution of the presidency over time! Today, we cover how the president’s power over war and authorizations for the use of force has changed since the founding.
The Expansion of War Powers
Over time, the presidency has gained new authorities to initiate war, engage in hostilities short of war, and direct the deployment of military forces for a wide variety of purposes. Congress and the president have enacted 11 separate formal declarations of war against foreign nations in five different wars. Congress and the president have also enacted 70 authorizations for the use of force (AUMF) without formal declarations of war. Several of these authorizations have been broad in scope (allowing operations in entire regions or the entire planet) and open-ended.
On their own initiative, presidents have directed our military forces to deploy hundreds of times. They have directed the military to deploy for combat, punitive expeditions, displays of force, the protection of U.S. interests in unstable situations, evacuations of citizens, military-to-military diplomacy, joint training exercises, disaster recovery, and humanitarian operations.
The Debate on War Powers
The expansion of presidential war powers has sparked a long-running debate. One position, favored by some originalist constitutional scholars, is that presidents are constitutionally required to obtain congressional authorization for any use of military force, except when directly responding to an attack. Others claim that the president has virtually unlimited constitutional authority to order the use of military force unilaterally. One argument from this camp is that whatever the founders thought about the distribution of war powers, a longstanding practice of unilateral presidential war-making has emerged since the Founding, especially after World War II. That practice, they argue, involves not only repeated, unilateral presidential uses of military force but also congressional acquiescence in that practice.
The Development of War Powers over Time
The first break from the originalist interpretation appeared when President Polk obtained congressional approval to go to war against Mexico in 1846 only after initiating hostilities in Texas against Mexico. The second and more permanent break from the originalist interpretation came when the Truman administration declared a police action in South Korea between June 1950 and July 1953. In 1961, without congressional approval, President Kennedy sent helicopters and troops to South Vietnam as part of secret operations against the Viet Cong. In 1964, Congress provided President Johnson an authorization for the use of military force in Vietnam but chose not to declare war formally. Congress repealed the authorization in 1971, but President Nixon chose to continue the military action, citing the Commander in Chief Clause, and expanded operations to include Cambodia and Laos.
President Polk was the first president to break from the originalist interpretation of the president's war powers.

Congress tried to pull back some de facto presidential war powers with the 1973 War Powers Resolution. The resolution allows the president to send the U.S. Armed Forces into action abroad only by declaration of war by Congress, by statutory authorization, or in case of an attack upon the United States, its territories, possessions, or armed forces. The resolution requires the president to notify Congress within 48 hours of committing armed forces to military action and forbids armed forces from remaining for more than 60 days, with a further 30-day withdrawal period, without congressional authorization for the use of military force (AUMF) or a declaration of war by the United States. The joint resolution has the force of law and was passed by two-thirds of both the House and Senate, overriding the veto of the bill by President Richard Nixon.
The Office of Legal Counsel has interpreted specific passages of the 1973 War Powers Resolution as recognizing a measure of unilateral presidential power. They point in particular to the Resolution's requirement that presidents either obtain congressional authorization within 60 days of introducing armed forces into hostilities or cease the operation. This provision, they claim, implicitly accepts a unilateral presidential authority to initiate military conflicts for less than 60 days in at least some circumstances. Once engaged, however, Congress may be reluctant to insist on maintaining its 60-day limit for fear of undermining a military action already in progress.
War Powers and Domestic Policy
Many of the president’s war-making authorities come with additional “standby” authorities that affect domestic policy. A declaration of war automatically provides the president and the Executive Branch with special powers. A declaration activates statutes that empower the president to interdict all trade with the enemy, to order manufacturing plants to produce armaments and seize them if they refuse, to control transportation systems in order to give the military priority use, and to command communications systems to give priority to the military. A declaration of war also triggers the Alien Enemy Act, which gives the president substantial discretionary authority over nationals of an enemy state who are in the United States. It activates authorities to use electronic surveillance for purposes of gathering foreign intelligence information without a court order under the Foreign Intelligence Surveillance Act. It automatically extends enlistments in the armed forces until the end of the war and can make the Coast Guard part of the Navy. It gives the president substantial discretion over the appointment and reappointment of commanders and allows the military priority use of the natural resources on the public lands and the continental shelf.
By contrast, an AUMF does not automatically trigger any of these standby statutory authorities. Some of them can come into effect if a state of war comes into being after authorization for the use of force is enacted. Most special powers, including many of the most sweeping ones, can be activated if the president chooses to issue a proclamation of a national emergency. Authorization for the use of force does not trigger any of these standby authorities, but the Office of the President asserted after the 2004 Hamdi v Rumsfeld case that it should.
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What's Next?
Tomorrow, we’ll guide you through how the president’s role in war and military action has changed over time.
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