The President’s War Powers

1. The Division of War Powers Between the Legislative and Executive Branches

In seeking to ensure that the fraught decision to go to war was not in the hands of any one person, the framers of the Constitution divided the war powers between Congress and the president. Article I grants Congress the authority to “declare war,” while Article II designates the president as “Commander in Chief of the Army and Navy,” assigning to the president the authority to conduct a duly authorized war.

This division of war powers was designed so that any decision to go to war could only be made with the widest possible political consensus. Only Congress, as the body most accountable to the American people, could, through a deliberative process, decide whether the nation chose war. As James Madison put it, “The constitution supposes, what the History of all Governments demonstrates, that the Executive is the branch of power most interested in war, and most prone to it. It has accordingly with studied care, vested the question of war in the Legislature.”

3. Congress’s Authority to Authorize Total War and the More Limited Use of Force

The “declare war” clause in Article I grants Congress the power to authorize the president to conduct both total war as well as more limited uses of force. Total war is authorized by a declaration of war, which provides the president with the entire and unqualified use of the U.S. military.

A declaration of war also activates a range of “standby statutory authorities,” which cover a range of powers, including warrantless surveillance and conscription. More limited uses of force are authorized by statutory force authorizations. The 2001 AUMF and 2002 Iraq AUMF are examples of such statutory force authorizations and are discussed in more detail below.

In 1800, the Supreme Court confirmed Congress’s authority to authorize the limited use of force in Bas v. Tingy. The Court unanimously held that Congress had lawfully authorized a limited, “imperfect” war or “Quasi-War” against France, through its passage of two statutory force authorizations, which authorized the president to use only the Navy, and for specified purposes. Congress has continued to authorize limited uses of force since this time. Indeed, a 2014 study of all declarations of war and statutory force authorizations found that 60% included a geographic limitation, 43% named the enemy, 37% limited the types of permissible operations, and 23% contained an expiration date.

5. The War Powers Resolution

What it says

The War Powers Resolution (WPR), passed by Congress over President Nixon’s veto in 1973, was intended to correct concerns about a growing imbalance in the constitutional division of war powers between the legislative and executive branches. It provides that the president can only introduce U.S. armed forces into hostilities or where hostilities are imminent if Congress has passed a declaration of war or specific statutory authorization (such as an AUMF) or where there is a “national emergency created by attack upon the United States, its territories or possessions, or its armed forces.”

The WPR requires the president to notify Congress of any hostilities conducted without a declaration of war within 48 hours (Section 4(a)) and provides that these hostilities must be terminated within 60 days of such notice (Section 5(b)). The WPR also includes a mechanism for Congress to order the termination of hostilities conducted without congressional authorization (Section 5(c)). 

While the WPR has often been misconstrued as an instrument that provides affirmative authority to the president to use force, this is not the case. Rather, the WPR provides a framework for the existing constitutional division of war powers between Congress and the executive branch, discussed above.

As the “Purpose and Policy” section of the WPR states, the intention of the resolution is “to fulfill the intent of the framers of the Constitution … and insure that the collective judgment of both the Congress and the President will apply to the introduction of United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances…”

The 60-day clock

The most prevalent misconception about the WPR concerns the requirement for the president to end foreign military actions after 60 days unless Congress specifically authorizes them. It is critical to note that this is not a “60-day free pass” for the president to use military force in any circumstances without congressional authorization. Any use of force by the president during these 60 days must fall within the parameters of the president’s defensive war power as Commander in Chief, discussed above. Any use of force that is not within these parameters and has not been authorized by Congress would be unconstitutional.

As a bipartisan group of legal scholars has discussed, “Beyond this range of defensive war powers, the burden lies on the President to obtain the authorization [from Congress before using force abroad].” As they further note, “The use of force for other than a limited range of defensive purposes is unconstitutional unless the President obtains advance congressional authorization.”

These scholars and other commentators have lamented this common misunderstanding surrounding the WPR’s 60-day clock. They note that rather than conferring any new power on the president to use force for 60 days, “the WPR expressly disclaims any intent to confer authority that presidents would lack in its absence.”

Indeed, the legislation is clear. The WPR does not give the president any power to use force without congressional approval. Rather, it provides a procedure to guide the existing division of war powers under the Constitution between Congress—as the body vested with the power to declare war—and the president, who, as Commander in Chief, retains a limited, inherent authority to defend the nation absent congressional approval in certain circumstances. 

Specific examples of the circumstances in which the president has authority to exercise such defensive war powers are discussed in the next section. 

Efforts to circumvent the WPR and the meaning of “hostilities”

Throughout the years since its enactment, presidents on both sides of the aisle have sought to circumvent the WPR’s requirement to end the use of force within 60 days in order to justify using lethal force abroad beyond this time limit without congressional authorization.  

One effort has been to claim that attacks against the same targeted group or country, sometimes within days of each other should be seen as discrete events that quickly start and conclude rather than part of a broader campaign of hostilities that would trigger the 60-day clock. This approach has been described as a “renewed clock” and “salami slicing.” Another effort has been to contend that U.S. forces were already in a particular area before hostilities commenced there and as such were never “introduced” into hostilities, eliminating the need to discontinue military force after 60 days.

A further attempt to avoid the WPR’s time limits has involved arguing that the use of lethal force by the U.S. military did not constitute “hostilities” at all. Examples include the 2013 Obama administration claim that U.S. airstrikes in Libya were not “hostilities” because the scope of the mission and risks of escalation and harm to U.S. forces were limited in nature. In 2026, the Trump administration also claimed that lethal strikes targeting boats in international waters allegedly carrying illegal narcotics were both part of an armed conflict while also not amounting to “hostilities,” citing a lack of risk of harm to U.S. service members.

These claims are incompatible with the intent of both the Constitution’s framers and that of Congress in passing the War Powers Resolution. The framers reserved only a limited defensive power to use force to the president, not the authority to conduct certain classes of lethal military operations and wars without congressional approval based on their anticipated harm to U.S. service members. Further, a House Foreign Affairs Committee report that accompanied the War Powers Resolution explained that the term “hostilities” was intended to apply to conduct that fell below the threshold of war:

The word hostilities was substituted for the phrase armed conflict during the subcommittee drafting process because it was considered to be somewhat broader in scope. In addition to a situation in which fighting actually has begun, hostilities also encompasses a state of confrontation in which no shots have been fired but where there is a clear and present danger of armed conflict.

In addition to this pre-enactment legislative history, Congress has also passed post-enactment resolutions under the WPR that broadly define “hostilities.” This includes the 2019 Yemen War Powers Resolution, which defined “hostilities” as including “in-flight refueling of non-United States aircraft conducting missions as part of the ongoing civil war in Yemen” and the 2020 Iran War Powers Resolution, which said that the targeted killing of Iranian general Qasem Soleimani by drone amounted to “hostilities.”

Finally, on numerous occasions, the executive branch has confirmed the understanding that “hostilities” can occur when there is minimal risk of harm to U.S. forces it its own 48-hour reports under the WPR. Examples include the Clinton administration’s 1998 strikes in Afghanistan and Sudan in response to al Qaeda’s bombing of U.S. embassies in Kenya and Tanzania, the Obama administration’s 2016 strikes on Houthi facilities in Yemen, and the first Trump administration’s strikes in 2017 and 2018 against the Syrian government in response to its use of chemical weapons.

As such, the claim that certain lethal military conduct falls below the level of force required by the term “hostilities” is contrary to the Constitution, the intent of Congress in passing the WPR, and subsequent congressional and executive branch practice.

7. Disagreement Between Congress and the Executive Branch over the Scope of Article II War Powers

While there is general agreement that the president’s Article II war powers permit the use of force without congressional authorization in the aforementioned circumstances, there remains significant disagreement over the scope of this power for other actions.

The executive branch has expressed an increasingly expansive view of its Article II war powers by reference to a two-part test: 1) “whether the President could reasonably determine that the action serves important national interests” and 2) whether the contemplated military action would “bring the Nation into a war.”

This test originated in a 1992 OLC memo and has most recently been used to justify the January 2020 strike that killed Iranian general Qassem Soleimani, the 2018 strikes against Syria, and the 2011 campaign of airstrikes against Libya. As scholars have discussed, the executive branch has not provided any criteria or limits for what constitutes a “national interest,” permitting the president to use military force without congressional authorization. As such, the national interests test “provides no meaningful constraint on presidential power.”

Congress, for its part, has never explicitly authorized the national interests test. Indeed, the last time that Congress legislated on the scope of the president’s Commander in Chief power to use force without congressional approval was the aforementioned War Powers Resolution, which provides that this power is limited to “a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.” Congress has also twice utilized the procedure in the WPR to order the termination of U.S. involvement in hostilities in respect of Yemen and Iran. These resolutions were vetoed by President Trump.