1. Introduction

In the wake of the September 11 attacks, the United States embarked on a global war on terrorism. As part of this global war, the United States also initiated a series of wars in countries across the Greater Middle East. Twenty years later, many of these wars continue with no end in sight. Among the wars the United States initiated as part of its larger war on terror was its war on al-Qaeda in Yemen, which would later brand itself as Al-Qaeda in the Arabian Peninsula (AQAP).

This report argues that “endless war” is a meaningful concept that is useful for understanding the counterterrorism war in Yemen. It defines endless war as a war in which a belligerent is pursuing objectives it cannot achieve but is also not at risk of being defeated or denied access to the battlefield. The U.S. record across three administrations suggests that the United States’ war in Yemen meets these criteria. The United States has too often sought unlimited objectives, seeking the complete destruction and defeat of AQAP or the al-Qaeda network more broadly.¹ Even if references to defeat are mere political rhetoric, such commitments have warped American strategy. On the other hand, when the United States has sought objectives short of AQAP’s destruction, it has failed to publicly describe the supposedly limited objectives in a clear and stable manner.

While there may have been a legitimate case for U.S. military action in Yemen in 2009, when AQAP almost brought down an airliner, nearly killing hundreds of people, the threat to the United States homeland from AQAP is substantially lower today. Continuing to wage war on AQAP in these circumstances risks embracing a military posture increasingly driven by preventive war logic in which war is justified based on the belief that war now is preferable to other options as a way of preventing growth in a rival’s capabilities that would pose a greater threat in a future war.²

Meanwhile, conditions in Yemen have deteriorated precipitously since 2009. Yemen faces an enormous humanitarian crisis while an internationalized civil war rages. This deterioration is rooted in local Yemeni political disputes and regional dynamics that cannot be reduced to the war on terror. However, pursuing a preventively framed counterterrorism war in such an environment is likely to further entangle the United States in local conflicts, constrain U.S. strategic options, and exacerbate the ongoing crises while also militarizing American politics.

Facing this situation, some analysts argue for greater commitment to the unlimited objective of defeating AQAP and the movements from which it arises.³ Others argue for the development of a sustainable counterterrorism strategy that acknowledges the problems with the objective of defeating AQAP but which seeks to maintain the ability to use military force for limited objectives in an open-ended manner.⁴ Both of these approaches are likely to backfire. Instead, the United States should define achievable limited objectives, where the accomplishment of an objective means an end to the war footing.

The U.S. counterterrorism war in Yemen has a long history. On November 3, 2002, the United States conducted its first drone strike in Yemen, killing six people as they drove across the desert of Yemen’s Marib province. The strike killed its target, Qaed Salim Sinan Al-Harithi, who was believed to have devised the 2000 attack on the USS Cole.⁵ It also killed an American citizen, Kamal Derwish, who allegedly recruited a group of Yemeni-Americans to train in camps in Afghanistan, where they met Osama bin Laden.⁶

The strike demonstrated that Yemen would, at times, be a battlefield in the larger global war on terror. However, facing backlash over the strike, the Bush administration tended to treat Yemen not as a battlefield but as a partner in the war on terror, focusing on advising and cooperating with the Yemeni government rather than directly carrying out strikes.⁷ The 2002 strike is the only one Bush is known to have conducted in Yemen.

In 2009, the Obama administration perceived an increasing threat from al-Qaeda in Yemen. As Obama took office, AQAP announced its formation via a merger of previously existing networks in Saudi Arabia and Yemen.⁸ Over the course of that year, Americans inspired in part, but not directed, by AQAP or by the propaganda of Anwar Awlaki, an American involved in AQAP’s attack plotting, killed 14 people in two attacks inside the United States.⁹ AQAP also conducted attacks in Yemen and Saudi Arabia. Over this same period, the United States prepared to carry out a campaign of direct, unilateral strikes against AQAP and to encourage the Yemeni government to escalate its own actions.¹⁰

The United States began carrying out a small number of strikes in December 2009 and early 2010. On December 25, 2009, Umar Farouk Abdulmuttalab, a Nigerian trained and directed by AQAP and Awlaki, attempted but failed to bring down a civilian flight over Detroit, using an innovative bomb designed to circumvent airport security. The attack sparked significant concern about AQAP as a global threat.¹¹ Over the next three years, that concern was amplified by two other, foiled plots to attack American aviation.

As a result, Yemen increasingly became the site of its own specific war between the United States and AQAP.¹² The war was embedded within the war against al-Qaeda, but also had its own identity. It combined direct U.S. air strikes with ramped-up efforts to train and equip the Yemeni government’s forces as well as other assistance. In 2011, the pace of U.S. strikes increased, reaching its peak under the Obama administration in 2012 amid AQAP’s territorial gains in the aftermath of the Arab Spring.¹³

In 2014 and 2015, conditions in Yemen worsened as a civil war between Yemen’s Houthi rebels and the Yemeni government broke out, leading to the functional collapse of the Yemeni government, and a Saudi and Emirati intervention backed by the United States. Initially, AQAP appeared to benefit from this instability, once again seizing territory.¹⁴ The Obama administration continued its strikes during this period. The Trump administration further escalated the pace of strikes to an unprecedented extent in 2017. Even as it escalated its own strikes, the United States sought to enable the counterterrorism efforts of its Saudi and Emirati partners.¹⁵

In the final years of the Trump administration, and as the Biden administration took office, the pace of strikes substantially declined and potentially halted.¹⁶ United States Central Command has not acknowledged conducting any strikes in Yemen in 2020 or 2021.¹⁷ However, that does not rule out covert strikes, and the U.S. government has more broadly acknowledged conducting strikes in Yemen in 2020.¹⁸ Reporting regarding the Biden administration’s review of counterterrorism strikes suggests a near total pause in 2021, although there are contested reports of U.S. strikes.¹⁹ Even with a possible pause, the U.S. counterterrorism war in Yemen has taken on an endless character rooted in a lack of clear and stable American objectives and the United States’ long-standing maintenance of an unlimited and likely impossible objective of destroying al-Qaeda. While the United States may have halted its strikes in Yemen, the state of war against AQAP continues. The United States has neither abandoned nor fully achieved its objectives. Nor has any administration declared the counterterrorism war in Yemen over.

The Biden administration’s move towards a vision of sustainable counterterrorism further institutionalizes this situation.²⁰ Even though the Biden administration appears to have abandoned unlimited objectives, it has not replaced them with clear statements of alternative achievable ends. The unlimited objectives that defined prior strategies can come to fill in as a projected end point, even if the administration remains largely silent about them.

As the United States claims to be adopting sustainable counterterrorism, the broader situation in Yemen remains a political and humanitarian disaster. The war has shown signs that it could escalate with the U.S. strike on an IRGC official in Yemen in 2020, and Houthi rebels firing ballistic missiles at the UAE in 2022, implicating American forces, being two examples.²¹ At the same time, the posture of endless war for rationales rooted in the futurology of preventive war logic undermines American democracy and the traditional moral restraints on warfare. Promulgating a vision of sustainable counterterrorism that retains the state of war underrates the potential for crises to collapse such a strategy and prevents the kind of strategic analysis of ends needed to navigate these treacherous conditions. Instead, the United States should develop a full policy platform aimed at ending its endless counterterrorism war—not sustaining it.

This report is divided into seven sections, including this introduction. The next section defines endless war and describes the dynamics that have made the U.S. war in Yemen endless. The third section assesses the threat that AQAP poses. The fourth section identifies the objectives the United States pursued in its war in Yemen and examines how a combination of expansive and unclear objectives helped generate the war’s endlessness. The fifth section analyzes whether U.S. objectives in Yemen are achievable. The sixth section analyzes the level of war termination planning. The concluding section discusses what it would take to sustainably end the war.