The United States has not formally declared war since 1942 when it did so against the Axis powers of Romania, Hungary, and Bulgaria during World War II. But since then, and despite numerous wars, military operations, and tens of thousands of battle deaths and casualties, the U.S. has not declared war.  

Instead, Congress has approved the use of military force via resolutions called authorizations for use of military force (AUMF).  

While AUMFs have a long history going back to America’s earliest days, their modern use has resulted in an expansion of presidential war powers and the sidelining of Congress and its important constitutional duty to declare war.  


What is an AUMF? 

An AUMF is a resolution passed by Congress authorizing the President to engage in hostilities that serves as an alternative to an official declaration of war.  

The process for passing an AUMF or a declaration of war is identical a resolution is introduced and voted on by both the Senate and House of Representatives and then signed by the president. Both an AUMF and declaration of war serve to authorize the president in his role as commander in chief to carry out military operations. 

However, there are crucial differences between what a declaration of war and an AUMF do in practice.  

A war declaration is a much more well-defined event against a specific country with narrower parameters and a more clearly defined enemy.   

In contrast, AUMFs have often been more open-ended and vague. An AUMF does not necessarily define which states are the enemy and, by extension, which states are not.  

For instance, the authority for the operations that became the Global War on Terror was based on an expansive interpretation of the 2001 AUMF. This authorization was originally intended to grant authority to respond to the 9/11 attacks in Afghanistan. Because the 2001 AUMF was vaguely written, the president and military leadership interpreted it as broadly as possible and the AUMF was ultimately used to support operations around the world without coming to Congress for additional approval.  

Some AUMFs have even been written to grant preemptive authority for military action, which turns Congress’ constitutional role on its head—our Founders never intended the President to have a “free pass” to initiate a war in the future whenever he or she chooses. 

The vagueness of an AUMF can also lead to unclear military objectives or the lack of a natural end to conflict, again, such as in the Global War on Terror.  

A war has a clearly defined end – a signed peace treaty between the nations. But if war is not declared and there is no peace treaty or a sunset date for the authorization, an AUMF can remain on the books and be used to carry out all manner of military operations that may be outside the scope for which the AUMF was intended.  

In fact, the last AUMF to be repealed was the Gulf of Tonkin Resolution in 1971, part of the process of bringing the Vietnam War to a close.  


What AUMFs are still current? 

There are currently four active AUMFs on the books with far reaching scopes and implications.  


1957 Middle East Force Resolution 

The oldest and longest active AUMF is the 1957 Middle East Force Resolution that was requested by the Eisenhower administration.  

This AUMF authorizes the president “to use armed forces to assist any such nation or group of such nations requesting assistance against armed aggression from any country controlled by international communism.”  

Decades on from the collapse of the Soviet Union, international communism is not a driving force in world politics, making this AUMF clearly obsolete.  


Authorization for Use of Military Force Against Iraq Resolution of 1991 

In January of 1991, President George H.W. Bush requested and received authorization from Congress to use military force to carry out United Nations Security Council Resolution 678 regarding Iraq’s invasion of Kuwait.  

Within months, Iraqi forces were crushed. However, the 1991 AUMF never had an expiration date and is still on the books, even though its purpose has long been achieved.  


2001 Authorization for Use of Military Force 

The 2001 AUMF was passed in the wake of the Sept. 11 terrorist attacks. While there was obviously a need to hunt down the perpetrators of this attack in Afghanistan and punish those who harbored them, the AUMF was written too broadly, enabling its abuse by presidential administrations to justify at least 41 military actions in 19 different countries. These far-flung operations have ranged from Afghanistan and Iraq, to Libya, Eritrea, the Philippines, and multiple countries in Central Africa.  

The specific language of the AUMF authorizes the president “to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons”. This already broad language has in turn been further broadened by executive interpretation to justify military actions against groups with little, if any, connection to the Sept. 11 attacks other than also engaging in terrorism.  

What’s more, the full list of groups and people that the 2001 AUMF has been used to justify military action against is currently considered classified information. This open-ended and secretive process without congressional oversight is a clear distortion of the separation of powers laid out in the Constitution. 


Authorization for Use of Military Force Against Iraq Resolution of 2002 

In 2002, amid increasing calls to depose the government of Saddam Hussein, Congress passed an AUMF authorizing the president to use military force to defend the U.S. from any threat posed by Iraq and enforce any UN Security Council Resolutions regarding Iraq.  

A few months later, under the auspices of this AUMF, the U.S. invaded Iraq in one of the most disastrous foreign policy blunders in American history.  

The Iraq War continued for over eight years, until the U.S. officially ended the mission in 2011. However, even though the operation officially ended, the AUMF remains on the books and efforts to repeal it have not been successful. American troops are still on the ground in Iraq to this day under a “train and equip” mission as part of an open-ended effort to assist Iraqi security forces.  


The move to repeal outdated AUMFs 

Force authorization resolutions go back to nearly the beginning of the country and in some cases are necessary for quick or more limited responses to actual threats.  

But AUMF usage has evolved from authorizations for minor military operations that would not amount to a full-blown war to justification for large military conflicts and interventions around the world with no clear objective or end.  

Currently, Congress is considering repealing some of these outdated AUMFs – specifically the 1957, 1991, and 2002 AUMFs. None of these AUMFs are the sole authority for any ongoing U.S. military operation, so both parties have focused attention on repealing them. 

An AUMF can be a valuable tool in the military arsenal, but it should never become a loophole to skirt Congress’ constitutional role in the war authorization process.