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

Seven years into a bloody civil war and twelve years into an intensive counterterrorism campaign in Yemen, the United States finds itself entangled in a messy regional proxy fight. The United States has been deeply compromised by its support for a Saudi-led coalition that has contributed to a horrific war, political instability, and the world’s worst humanitarian crisis. As we approach the seventh anniversary of the Saudi-led intervention in Yemen, it is no longer clear why the United States is fighting or how the use of force will promote U.S. and regional security interests. What is clear is that U.S. operations in Yemen have contributed to the current unstable situation, and that military force alone will not bring peace to the country or secure the United States from the threats it sought to counter in the first place.


The United States has been involved in an armed conflict with al-Qaeda and affiliated groups in Yemen arguably since the October 2000 bombing of the USS Cole off the coast of Yemen, at the time one of al-Qaeda’s most significant attacks. However, Yemen did not become a first tier front in the U.S. counterterrorism campaign until 2009. In the intervening years, al-Qaeda elements in Yemen and Saudi Arabia united under seasoned leadership that had trained with Osama bin Laden to form al-Qaeda in the Arabian Peninsula (AQAP). On Christmas Day 2009, the group supplied Umar Farouk Abdulmutallab with an ingeniously designed explosive device concealed in his underwear in an attempt to bring down an airliner en route to Detroit, Michigan. The device malfunctioned and the crisis was averted, but the U.S. government sprang into action, launching a military campaign against AQAP in Yemen that continues to this day.

In the early days of the campaign, the United States struggled to establish an effective counterterrorism program, and AQAP plotted at least two additional aviation attacks that were disrupted shortly prior to execution, all while building strength on the ground in Yemen. At the same time, the group’s charismatic Yemeni-American propagandist, Anwar al-Aulaqi, and another American, Samir Khan, produced a series of videos and online publications recruiting disaffected young men to their cause and providing instruction on how they could carry out attacks back home.

Yemen’s longtime president, Ali Abdullah Saleh, proved to be a highly erratic partner, and the United States struggled to develop effective counterterrorism assistance or a consistent lethal strike campaign. However, in 2012, the Arab Spring came to Yemen, taking down Saleh in the process and replacing him with a far more pliant counterterrorism partner, Abdrabbuh Mansur Hadi. Hadi embraced the United States and, over the next two and a half years, the United States conducted one of its most intense counterterrorism campaigns in Yemen. The United States flooded Yemen’s government with weapons and trained its commando forces. U.S. Special Operations Forces (SOF) embedded with a range of Yemeni forces and enabled their operations. Yemeni forces flushed AQAP out of its strongholds across southern and central Yemen. Dozens of U.S. targeted airstrikes killed a series of AQAP’s top operatives, including Aulaqi and Khan.

But Hadi handled Yemen’s internal politics poorly and, in late 2014, the Houthis–a predominantly Zaydi Shi’a Islamic religious-political-armed movement from northern Yemen– swept into Sana’a and overthrew the Yemeni government. The United States shuttered its embassy in Sana’a and maintained only a small, episodic presence in Aden. In 2015, Saudi Arabia initiated what has become a disastrous and brutal campaign against the Houthis – a campaign the United States has supported, including by supplying weapons, providing mid-air refueling, and offering targeting assistance. Iran, meanwhile, has provided support to the Houthis, turning Yemen into the site of a proxy war between regional and global adversaries.

Most terrorism watchers assumed AQAP would seize on the chaos to develop a new safehaven. And for a time this is what happened–as AQAP took territory in Mukallah, in eastern Yemen, the group stole millions from its central bank and levied millions more in taxes from running Yemen’s third largest port. Islamic State (IS) elements also emerged in Yemen, and they appeared to enjoy a tenuous truce with AQAP before the groups eventually turned on one another. But all of that changed when Emirati forces, backed by U.S. advisors and air strikes, took the fight to AQAP. Working with local fighters and employing a brutal set of tactics that included extensive torture of prisoners, the Emiratis drove AQAP from Mukallah. They later attacked AQAP in smaller strongholds across the south. Speculation emerged that the United Arab Emirates (UAE) and/or Saudi Arabia were also paying off AQAP, enlisting it in the fight against the Houthis.

Current U.S. Involvement in Yemen

A surge of U.S. airstrikes against AQAP and IS throughout the early years of the Yemeni civil war has now slowed to a trickle. U.S. airstrikes from 2015-2018 degraded AQAP’s leadership, removing its top leaders and external operational experts (including the mastermind of the concealed explosive devices), and supported the UAE in dislodging AQAP from its strongholds. But since 2019, the United States has conducted an average of only about a half dozen strikes per year, including just two reported last year.

According to Biden’s December 2021 periodic report pursuant to the War Powers Resolution, “a small number” of U.S. military forces are deployed to Yemen to conduct operations against AQAP and IS and to work with the Hadi government and regional partner forces. However, infighting among anti-Houthi forces has complicated partnered counterterrorism efforts. The United States continues to back the Hadi government, but southern leaders have organized into the Southern Transitional Council (STC), which has challenged Hadi’s rule and has eclipsed his government as the dominant non-Houthi power in the country. The UAE has soured on Hadi and primarily partners with the STC, though it has fewer counterterrorism forces and conducts less operations in Yemen than before. The U.S. military has publicly disclosed few additional details on the numbers or activities of U.S. forces in Yemen or the range of partners they work with.

AQAP and IS are in shambles, with both groups having suffered major defeats at the hands of local forces, the UAE, U.S. airstrikes, and Houthi forces. AQAP’s current leader, Khaled Batarfi, is known as a far weaker leader than his predecessors and has failed to rebuild the organization after its losses. IS has been largely routed. Yet Yemen’s civil war rages on, and many of the extremists who would likely fight with AQAP or IS, if either group regains its footing, have taken up arms against the Houthis. When Yemen’s civil war ends, and absent an effort at reintegrating fighters, a cadre of seasoned extremist militants could flow back into IS or AQAP’s ranks.

As to Yemen’s civil war, shortly after taking office, U.S. President Joe Biden announced that he was “ending all American support for offensive operations in the war in Yemen, including relevant arms sales.” Yet subsequent reporting made clear that U.S. support continued in the form of “defensive” support, including servicing Saudi aircraft and providing other logistical and intelligence support. Critics maintain that this amounts to continued support – albeit indirect – for Saudi operations in Yemen.

The Legal Basis for U.S. Involvement

The United States involvement in Yemen–and the legal basis for that involvement–has been the subject of criticism for years.

We begin with the counterterrorism operations: As a matter of domestic law, the operations against AQAP rest primarily on the 2001 Authorization for the Use of Military Force (AUMF), which is the central authority cited by the U.S. government for counterterrorism operations against al-Qaeda and “associated forces,” including AQAP and ISIS, in Yemen. While there has been substantial debate about the importance of repealing and replacing the woefully out-of-date AUMF, there is general agreement within the executive branch that this use of the existing authority falls squarely within the use of the AUMF under multiple presidents.

As a matter of international law, counterterrorism operations against al Qaeda and its “associated forces” – including AQAP and IS – in Yemen and around the region have long rested on two bases: consent of the host state and, where that consent is absent, self defense under Article 51 of the UN Charter (combined with a controversial argument that the territorial state involved is “unable or unwilling” itself to effectively suppress the terrorist threat). Hadi remains the internationally-recognized president of Yemen, even though he has resided in Saudi Arabia since 2017. His consent to U.S. and Saudi operations in the country have provided a fig leaf of legal legitimacy, but there remain longstanding, unaddressed concerns about the validity of that consent.

Turning to the U.S. role in Yemen’s civil war: Critics have raised substantial concerns about the absence of domestic legal authority for U.S. support for the Saudi-led coalition’s operations aimed primarily at Houthi rebels. The Houthis, after all, are not an “associated force” of al-Qaeda. To the contrary, they have been engaged in regular fighting against AQAP for years. Hence the U.S. role in the conflict against the Houthis cannot reasonably be said to fall within the scope of the 2001 AUMF. Members of Congress repeatedly sought to force President Trump to withdraw U.S. support for the coalition. On Feb. 28, 2018, for example, Senator Bernie Sanders (I-VT) introduced a joint resolution pursuant to the War Powers resolution calling for the removal of U.S. armed forces from hostilities in Yemen that had not been authorized by Congress. That resolution specifically asserted that U.S. forces had been introduced into hostilities “including providing to the Saudi-led coalition aerial targeting assistance, intelligence sharing, and mid-flight aerial refueling.” It made clear that such introduction of armed forces into hostilities had not been authorized by Congress and therefore violated the War Powers Resolution. That joint resolution failed by a vote of 55-44, but it brought attention to the questionable domestic legal authority for U.S. military support for the Saudi-led coalition, and it helped prompt a series of related resolutions, including a 2019 resolution to end U.S. support for Saudi operations in Yemen that passed both houses of Congress only to be vetoed by then-President Trump.

President Biden’s announcement that the United States would no longer provide “offensive” support for Saudi military operations in Yemen likely brings this chapter to a close, for now. But continued servicing of Saudi jets and other “defensive” support could reignite such legal concerns.

The end of (most) U.S. support for the Saudi-led coalition also brings to a close some of the key concerns under international law. Like the counterterrorism operations, the Saudi-led operations against the Houthis have been justified by Hadi’s “consent.” Yet while this helped paper over worries about jus ad bellum violations, there were independent concerns about ongoing jus in bello violations. Indeed, the Saudis and Emirates have been accused of various war crimes in the course of the brutal war against the Houthis. A 2018 report by the United Nations Panel of Experts on Yemen, for example, documented many violations of international humanitarian law. The end of offensive military support for the Saudi-led coalition helps ease concerns about ongoing U.S. complicity in those war crimes, yet critics still argue that the United States, by continuing some support to Saudi Arabia and failing to condemn its policies in Yemen, is still contributing to the humanitarian crisis in the country.

What now?

This brings us to a final question: Where do we go from here? A year after signaling a new approach in Yemen, the administration’s progress remains uneven, at best. President Biden has addressed some of the most pressing legal concerns by withdrawing direct offensive military support for the Saudi-led coalition’s military operations in Yemen. However, questions remain about residual U.S. support to the Kingdom. What does it mean, for example, to curtail “offensive weapons” sales and what counts as a “defensive weapon”? The civil war in Yemen and continued U.S. support for the Saudi government remain concerning, particularly given the dire situation of the population – ravaged by war, the worst cholera outbreak in modern history, the COVID-19 epidemic, and now a blockade that has led to starvation in parts of the country. The appointment of a senior career diplomat as Special Envoy for Yemen signaled the Biden administration’s intent to prioritize resolving the conflict, but the administration has struggled to gain traction with regional powers and to marshal the full power of the U.S. government toward a peace agreement. Meanwhile, tensions with Saudi Arabia and UAE over the restrained Washington response to Houthi attacks in both countries, along with other issues, has undermined U.S. efforts to rally Middle Eastern partners to the defense of Ukraine against Russian aggression. Some members of Congress, meanwhile, have continued to express interest in bringing the conflict to an end, though partisan divisions on whether to hold Saudi Arabia accountable have hampered Congress’ ability to impose additional constraints on U.S. policy. At the end of the day, it seems likely that more of the onus for resolving the Yemen conflict will lie with the administration than the Hill.

The United States must press for a negotiated end to the conflict, though it is clear that any road to negotiations will be long and fraught. Most recently, the Saudi-based Gulf Cooperation Council invited the warring sides for talks in Riyadh. But the Houthis rejected the offer and then launched a series of drone and missile strikes on natural gas and desalination plants in Saudi Arabia.

As to the counterterrorism campaign, Yemen remains one of many longstanding fronts in the “forever war.” With AQAP and IS in Yemen degraded, that war is relatively quiet for now. Given the reduced terrorist threat and the stain of U.S. involvement in the Saudi campaign, the Biden administration should resist ramping back up military operations. The bigger terrorism threat is what may come after the civil war ends. Years of war have left the country without any effective governance. Many of those who have fought the Houthis are young men partly motivated by religious or sectarian concerns, who may join violent extremist groups after the civil war ends. This leaves Yemen vulnerable to the resurgence of al-Qaeda, IS, or successor groups.

Even though a peace agreement in Yemen may still be a long way off, U.S. policymakers should already be thinking about a counterterrorism program built on civilian tools. Building some semblance of effective governance after the civil war and developing interventions targeted at mitigating violent extremism and reintegrating fighters must be top priorities for U.S. policy. A resumption of significant military operations against terrorist groups in Yemen is unlikely to sustainably address the threat and indeed may disrupt any fragile peace that can be achieved. In short, a campaign of lethal strikes against AQAP or other terrorist groups in Yemen will do little, on its own, to achieve U.S. and regional security goals.

The question for the United States in Yemen, and similar places, is whether it is prepared to invest in the institution building and civilian-led interventions that would truly insulate the country from the resurgence of terrorist threats. As long as the answer is no, the threat of renewed violence – and perpetual war – remain.

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).