Editors’ note: This article is the third installment in our Still at War symposium, which can be accessed here

In the first year of the Biden administration, the United States has wound down elements of its military operations against ISIS, al-Qaeda, and certain affiliates – commonly referred to as the “war on terror” – notably completing the withdrawal of U.S. forces from Afghanistan and significantly reducing airstrikes in Somalia. At the same time, the administration continues to conduct occasional strikes, including in Syria and Somalia, and has left in place much of the legal, institutional, and physical infrastructure that underpin this decades-long conflict. A future president – or this one – therefore would have the necessary tools to once again unilaterally ramp up hostilities, just as prior administrations of both parties dramatically expanded the conflict by stretching the 2001 Authorization for Use of Military Force (2001 AUMF) to apply to a broad array of actors and locales. One region where this could happen is the Sahel, where limited U.S. operations continue, generally in support of partner forces, although it is unclear whether there is any direct threat of external attacks against the United States by the groups U.S. partners are fighting. Despite the lack of clarity regarding core U.S. national security interests, the pieces remain in place for an expansion of the war on terror in the Sahel should this or a future administration so decide.

A Brief History of the Ever Expanding AUMF

As detailed in the Crisis Group report, Overkill, the spread of the war on terror has for two decades been driven by the executive branch.

The 2001 AUMF authorizes the president to use 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.” Although Congress clearly intended the authorization to apply to the perpetrators of the 9/11 attacks and those that harbored them, namely al-Qaeda and the Taliban, the executive branch has relied on creative interpretations to effectively sever that connection and to unilaterally stretch the 2001 AUMF.

Such interpretations have included the theory spawned by the executive branch during the George W. Bush and Barack Obama administrations that the 2001 AUMF authorizes force against “associated forces” of al-Qaeda—an elastic term that does not appear in the statute itself. (Congress eventually endorsed the concept of associated forces in the National Defense Authorization Act for Fiscal Year 2012 (2012 NDAA), but did not speak to the executive’s assessment of which groups so qualify). Although the executive branch used the concept of “associated forces” early on in order to justify the detention of non-al-Qaeda, non-Taliban detainees at Guantanamo Bay, it later repurposed the concept in order to use lethal force against groups far removed Afghanistan’s battlefields such as Al Shabaab in Somalia.

The Obama administration innovated further when it concluded that the AUMF authorizes the use of force against the Islamic State even though the group split from al Qaeda and therefore does not appear to fit within the definition of associated forces. The Trump administration subsequently used these theories to include new “associated forces,” such as al-Qaeda in the Islamic Maghreb (AQIM) as well as Islamic State affiliates in Yemen and Somalia, into the 2001 war authorization’s scope.

At the same time, during the Obama and Trump administrations U.S. special operations forces deployed on what are described as “advise, assist, and accompany” operations in a number of African countries have quietly expanded the war on terror’s scope from the ground up. These operations were sometimes conducted in connection with a statute – 10 U.S.C. §127e – that authorizes the Pentagon to spend appropriated funds in support of foreign counterterrorism forces, including irregular groups or individuals. Although not a use of force authorization, according to a former U.S. official, in practice the Pentagon used 127e to create “clear, unambiguous proxies of the United States,” which U.S. forces could then partner with on combat operations.

With limited consultation even within the executive branch, these forces engaged in ground combat and sometimes called in airstrikes, often under the rubric of self-defense or collective self-defense of local partner forces. (Such “self-defense” strikes were exempt from the higher-level approval procedures for strikes imposed by the counterterrorism policy frameworks of the Obama and Trump administrations.) Across Africa, the executive branch failed to report many of these incidents of “collective self-defense” to Congress as seemingly required by the War Powers Resolution for actions taken without prior congressional authorization (that is relying only on the authority of Article II of the Constitution). Instead, as with al-Shabab in Somalia, the executive branch has sometimes adopted a “shoot first and apply the AUMF later” approach, whereby legally questionable combat operations, including airstrikes, are then deemed retroactively to have been covered by the 2001 AUMF.

The Biden administration, like its immediate predecessor, treats the full list of groups covered by the 2001 AUMF as classified. Moreover, although the executive branch has articulated a standard for what constitutes an “associated force” of al Qaeda, it has not explained the standards for assessing whether an ISIS affiliate is “ISIS” for the purposes of the 2001 war authorization. Thus, the public is left in the dark as to who the United States is at war with and what criteria the executive branch might use to expand that war.

The War on Terror in the Sahel

The Sahel looms especially large in the future of the war on terror, due to the prominence of a number of jihadi groups, the presence of U.S. troops supporting partner forces (particularly France), a history of occasional combat, and perhaps most significantly, an existing infrastructure for U.S. operations.

The United States has supported French counterterrorism efforts in the Sahel since 2013, including by providing airlift of French troops into Mali, providing aerial refueling, and the sharing of intelligence. It was to support intelligence collection and sharing with France that combat-equipped U.S. armed forces deployed to Niger in 2013.

In addition to such non-kinetic support for counterterrorism operations by partners, U.S. armed forces have sometimes engaged in combat in the Sahel. The 2017 attack at Tongo Tongo, Niger by ISIS Greater Sahara, which killed four U.S. soldiers, may have been the most prominent such incident, but it was by no means the only one. U.S. forces, sometimes deployed on so-called “advise, assist, and accompany” missions with foreign partners, have engaged in combat elsewhere in Niger, as well as in Mali and Cameroon against both ISIS and al-Qaeda- linked jihadists. As recently as January 2022, a U.S. service member co-located with French troops in Gao, Mali was injured in a mortar attack that killed one French soldier. The Pentagon has not publicly identified the group responsible for that latest attack.

While acknowledging that they are not direct threats to the United States, General Townsend, the commander of U.S. Africa Command in recent testimony before the Senate Armed Services Committee characterized “the metastasis of Al-Qaida and ISIS in West Africa…[as] a clear danger to U.S. persons and interests in West Africa as well as our African and international partners there.” In an interview with Voice of America he identified three jihadi groups as being of particular concern to the United States: Townsend described JNIM as “the Sahel arm of al-Qaida in the Islamic Maghreb” and “part of corporate al-Qaida.” Townsend also cited two ISIS affiliates, ISIS Greater Sahara and ISIS West Africa Province, as regional threats. As the full list of entities covered by the 2001 AUMF is classified, it is unclear which of these groups the executive branch deems covered by the war authorization though, as described below, U.S. forces previously have used force against some of them, including ISIS Greater Sahara and ISIS West Africa Province. Townsend’s characterization of JNIM’s connection to AQIM may also be significant given that the Trump administration previously deemed AQIM to be covered by the AUMF.

Over 800 U.S. troops are deployed in Niger (roughly comparable to the number in Syria) and an unspecified number of additional troops are deployed to the broader Sahel region. Townsend and other officials continue to couch U.S. military operations in the region primarily in terms of supporting partners, including through training, equipping, logistics (such as aerial refueling), and intelligence sharing. (The U.S. is reported to have provided some intelligence used to help track Adnan Abu Walid al-Sahraoui, the leader of ISIS-Greater Sahara, prior to France’s lethal strike on him in 2021).

Should this or a future administration wish to ramp up operations, the infrastructure is there to do it. The troop presence, as noted, is significant. Moreover, sitting like Chekov’s gun outside of Agadez, Niger is a large, recently completed airbase hosting U.S. drones. Although these drones are currently used for intelligence, surveillance, and reconnaissance (ISR), gathering information to be shared with partners, particularly France, some of the drones are also armed. (At least two U.S. drones armed with Hellfire missiles have crashed in Niger).

In the context of my Crisis Group research, former U.S. officials characterized the airbase at Agadez as a direct action facility in search of a mission. (“Direct action” is a term that encompasses lethal action, such as through drone strikes, and capture operations.) Another former official explained that basing for strike aircraft is the “untold story of U.S. direct action” in the war on terror. This official described a cascade dynamic in which first U.S. forces are deployed on an “advise, assist, and accompany” mission, which then increases the perceived threat to those U.S. forces as their numbers grow, creating a perceived need for air assets to protect the U.S. troops, an airbase is built, and then inevitably the newly available aircraft are used for strikes, often under the rubric of “self-defense” or “collective self-defense” of partner forces. Indeed, “collective self-defense” strikes against alShabaab in Somalia, beginning in 2015, were only possible because of the availability of such air assets.

A U.S. official interviewed by Crisis Group observed that “once you have the facility, you want to use it or the host government wants you to use the capabilities on their behalf.” Even if U.S. forces in Niger themselves mostly remain behind the wire, these drones could be used for “collective self-defense” strikes on behalf of partner forces as U.S. Africa Command continues to do in Somalia. Partner forces eligible for “collective self-defense” strikes are apparently designated by the Commander of U.S. Africa Command, though the standards for such designations are unclear. As with the full list of groups covered by the 2001 AUMF, the identities of any such “combatant-commander designated partner forces” in the Sahel are not publicly known.

Current and former officials also cited the risk that the airbase at Agadez would itself become a target for jihadists, akin to al-Shabaab’s 2020 attack on the airfield at Manda Bay, Kenya.

What Now?

The Biden administration has not expressed any interest in using military force in the Sahel. Nonetheless, there are reasons to be watchful of U.S. operations in the region. Hundreds of U.S. troops are located in an area of ongoing conflict, with a history of sporadic U.S. combat. These forces now have greater strike capabilities in the form of armed drones. And of course, the executive branch can as a practical matter decide for itself against whom to wage war, unchecked by Congress. Taken together, these factors raise the specter of future U.S. hostilities in the Sahel.

In one scenario, U.S. operations in the Sahel could follow the model of the war on terror’s expansion in Somalia, where ostensibly non-combat operations transitioned into U.S. direct action under the guise of collective self-defense of partners. Consistent with past practice, the executive branch may unilaterally expand the 2001 AUMF further to cover additional jihadi groups in the Sahel, rather than seeking specific congressional authorization for war in the region.

A unilateral expansion of the war on terror in the Sahel is, however, the wrong approach. Shoehorning jihadi groups operating in the Sahel into a war authorization intended for the perpetrators of the 9/11 attacks risks obscuring the local roots of these armed groups and inaccurately imputing international ambitions to these actors. Moreover, greater reliance on military tools is unlikely to deliver sustainable stability to the region.

The Biden administration’s focus understandably is devoted to other, more pressing foreign policy crises, first and foremost Russia’s war on Ukraine. As a matter of policy, the White House has placed the global war on terror on the backburner and dialed operations down to a low simmer (the White House has yet to finalize and publicly release its policy framework for counterterrorism direct action). Yet, the testimony of executive branch witnesses at a recent hearing before the House Foreign Affairs Committee suggests that the administration is not yet prepared to seriously engage with Congress on durably curtailing the war by revising and carefully tailoring the expansive and outdated text of the 2001 AUMF.

That is a mistake. To forestall another twenty years of the war on terror, the administration should be more transparent about how it currently interprets the 2001 AUMF and more earnestly devote itself to working with Congress on concrete measures to rein in this antiquated war authorization. For its part, Congress should reclaim its war powers so that it, rather than the executive branch, determines against whom and where the United States is at war and imposes a sunset on any future use of force authorization.

Without such legislative reform, the White House will bequeath to another administration the loaded weapon of the 2001 AUMF. If the history of the war on terror is any guide, the Sahel may be its next battlefield.

Image: US vehicle is pictured at a military base in Rumaylan (Rmeilan) in Syria’s northeastern Hasakeh province on July 28, 2020 (Photo by DELIL SOULEIMAN/AFP via Getty Images).