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Yemen: Civil War and Regional Intervention



This report provides information on the ongoing crisis in Yemen. Now in its fourth year, the war in Yemen shows no signs of abating and may be escalating. In recent weeks, the northern Yemeni armed militia and political movement known as the Houthis have launched several missile attacks into Saudi Arabia, while the Saudi-led coalition, a multinational grouping of armed forces primarily led by Saudi Arabia and the United Arab Emirates (UAE), has continued to conduct air strikes inside Yemen. Including combatants, the war in Yemen may have killed more than 10,000 Yemenis and has significantly damaged the country's infrastructure. As the war continues, the risk of it spreading beyond Yemeni territory appears to be growing.

Yemen is considered one of the world's worst humanitarian disasters. According to the United Nations Office for the Coordination of Humanitarian Affairs (UN OCHA), out of a total population of nearly 30 million people, 22 million Yemenis are in need of humanitarian assistance. Since March 2015, the United States has been the largest contributor of humanitarian aid to Yemen. The United States has provided a total of $854.223 million in humanitarian assistance in FY2017 and FY2018.

For additional information on Yemen, including a summary of relevant legislation, please see CRS Report R45046, The War in Yemen: A Compilation of Legislation in the 115th Congress, by Jeremy M. Sharp and Christopher M. Blanchard and CRS Insight IN10866, Joint Resolution Seeks to End U.S. Support for Saudi-led Coalition Military Operations in Yemen, by Christopher M. Blanchard, Jeremy M. Sharp, and Matthew C. Weed.

Conflict Overview

Now in its fourth year, the war in Yemen shows no signs of abating and may be escalating. In recent weeks, the northern Yemeni armed militia and political movement known as the Houthis |1| (Ansar Allah in Arabic) have launched several missile attacks into Saudi Arabia, while the Saudi-led coalition, a multinational grouping of armed forces primarily led by Saudi Arabia and the United Arab Emirates (UAE), has continued to conduct air strikes inside Yemen. According to the Yemen Data Project, the coalition has conducted over 16,000 air strikes in Yemen since 2015. |2|

On March 25, 2018, the third anniversary of the start of hostilities, the Houthis launched seven ballistic missiles at Saudi Arabia, killing at least one person. On April 2, a Saudi-led coalition air strike on the Houthi-controlled port city of Hodeidah killed more than 14 civilians, including children. A day later, the Houthis fired on a Saudi oil tanker in the Red Sea, causing minimal damage to the vessel, though it reignited fears over security in the Red Sea and the Bab al Mandab strait, one of the world's maritime chokepoints. |3| On April 11, the Houthis fired a missile directed at the defense ministry in Riyadh, marking the fourth time they have targeted the Saudi capital. Including combatants, the war in Yemen may have killed more than 10,000 Yemenis and has significantly damaged the country's infrastructure. |4| As the war continues, the risk of it spreading beyond Yemeni territory appears to be growing.

Figure 1. Lines of Control in Yemen

Source: Graphic created by CRS. Map and information generated by Hannah Fischer using data from Risk Intelligence (2018); Esri (2017 & 2018); NOAA (2018); USGS (2018); Department of State (2015).

Although both the Obama and Trump Administrations have called for a political solution to the conflict, the wars' combatants still appear determined to pursue military victory. They also would appear to fundamentally disagree over the framework for a political solution. The Saudi-led coalition demands that the Houthi militia disarm, relinquish its heavy weaponry (ballistic missiles and rockets), and return control of the capital Sana'a to the internationally-recognized government of President Abdu Rabbu Mansour Hadi, who is in exile in Saudi Arabia. The coalition cites international consensus for these demands, insisting that the conditions laid out in United Nations Security Council Resolution (UNSCR) 2216 (April 2015) should form the basis for a solution to the conflict. |5| The Houthis reject UNSCR 2216 and seem determined to outlast their opponents while consolidating their control over northern Yemen. Since the December 2017 Houthi killing of former president Ali Abdullah Saleh, a former Houthi ally, it would appear that there is no single Yemeni rival to challenge Houthi rule in northern Yemen.

The prospects for returning to a unified Yemen remain dim. According to a recent United Nations report, "The authority of the legitimate Government of Yemen has now eroded to the point that it is doubtful whether it will ever be able to reunite Yemen as a single country." |6| While the country's unity is a relatively recent historical phenomenon (dating to1990), the international community had widely supported the reform of Yemen's political system under a unified government just a few years ago. In 2013, Yemenis from across the political spectrum convened a National Dialogue Conference aimed at reaching broad national consensus on a new political order. However, in January 2014 it ended without agreement, and the Houthis, rather than accepting the dialogue's outcome, went to war.

Yemen at the United Nations

Figure 2. Martin Griffiths, New U.N.Special Envoy for Yemen

Martin Griffiths

Source: Office of the Special Envoy of the Secretary-General for Yemen.

In March 2018, Martin Griffiths of the United Kingdom assumed the role of Special Envoy of the United Nations (U.N.) Secretary General for Yemen, replacing Ismail Ould Cheikh Ahmed, who despite multiple attempts at reaching a settlement, was unable to make headway toward a peace deal. Upon his exit, Ahmed ultimately blamed the Houthis for obstructing peace, declaring that their inability to make concessions on security arrangements was the key stumbling block in negotiations. |7| On March 15, the U.N. Security Council issued a presidential statement on Yemen, which, among other things, welcomed Griffiths' appointment while calling "upon all parties to the conflict to abandon pre-conditions and engage in good faith with the UN-led process..." |8|

In January 2018, the United National Panel of Experts on Yemen concluded that Iran was in non-compliance with UNSCR 2216 for failing to prevent the transfer to Houthi forces of Iranian-made short range ballistic missiles. |9| On February 26, 2018, Russia vetoed a draft U.N. Security Council resolution that would have expressed U.N. concern that Iran is in non-compliance with the international arms embargo created by UNSCR 2216. The Security Council did pass a new resolution (UNSCR 2402) that renewed for a year UN sanctions first imposed by UNSCR 2140 (2014), such as a travel ban and asset freeze on designated Houthi leaders and the former (and now deceased) president Ali Abdullah Saleh. UNSCR 2402 also renewed the arms embargo against Yemen, first imposed by UNSCR 2216.

Iranian Support to the Houthis

Although Houthi militia forces are likely not solely dependent on Iran for armaments, financing, and manpower, after three years of war, most observers agree that Iran |10| and its Lebanese ally Hezbollah have aided Houthi forces with training and arms shipments. |11| In 2016, one unnamed Hezbollah commander interviewed about his group's support for the Houthis remarked "After we are done with Syria, we will start with Yemen, Hezbollah is already there....Who do you think fires Tochka missiles into Saudi Arabia? It's not the Houthis in their sandals, it's us." |12| In repeated public statements by high-level Saudi officials, Saudi Arabia has cited Iran's illicit support for the Houthis as proof that Iran is to blame for the Yemen conflict. In many ways, this has become a self-fulfilling prophecy; as the war has continued, there have been more frequent reports and allegations of Iranian involvement in Yemen. Overall, while Iranian aid to the Houthis does not match the scale of its commitments to proxies in other parts of the Middle East, such as in Syria, Lebanon, and Iraq, it would seem to be a relatively low-cost way of keeping Saudi Arabia mired in the Yemen conflict. At the same time, Iran had few institutionalized links to the Houthis before the civil conflict broke out in 2015, and questions remain about the degree to which Iran and its allies can control or influence Houthi behavior.

Figure 3. Figure 2. Houthi-Saleh Forces Display the "Burkan-2" Missile

Burkan-2 Missile

Source: Source: An image released by the pro Houthi-Saleh SABA News Agency on February 6, 2017, Jane's Defence Weekly, February 8, 2017.

Prior to the 2015 conflict, the central government in Yemen had acquired variants of Scud-B missiles from the Soviet Union and North Korea. The Houthis seized these missiles during their seizure of the capital. Since 2016, the Houthis have been firing what they call the "Burkan" short-range ballistic missile (claimed range of 500-620 miles) into Saudi Arabia (the latest version is the Burkan-2H). In November 2017, after the Houthis fired a Burkan-2H deep into Saudi Arabian territory, the Saudi-led coalition and U.S. officials said that the Burkan-2H is an Iran-manufactured Qaim missile. |13| In a hearing before the House Armed Services Committee, Commander of United States Central Command (CENTCOM) General Votel remarked that "Certainly, as we've seen with Ambassador Haley and her demonstration, most recently, with some of the items recovered from Saudi Arabia, these weapons pose the threat of widening the conflict out of... Yemen and, frankly, put our forces, our embassy in Riyadh, our forces in the United Arab Emirates at risk, as well as our partners'....As we look at places like the Bab-el-Mandeb, where we see the introduction of coastal defense cruise missiles, some that have been modified, we know these are not capabilities that the Houthis had. So they have been provided to them by someone. That someone is Iran." |14|

Saudi Security Concerns, Military Operations, and U.S. Support |15|

Saudi concerns about the Houthis, and about the security of Yemen more broadly, predate the current conflict and have been reflected in a series of political, financial and security interventions over several decades. Saudi leaders expressed increasing alarm about Houthi advances during 2014 and demanded that the international community act to prevent the overthrow of the Hadi government. In March 2015, Saudi Arabia and members of a Saudi-led coalition launched a military campaign in response to a specific request from President Hadi "to provide instant support by all necessary means, including military intervention to protect Yemen and its people from continuous Houthi aggression ...and to help Yemen in the face of Al Qaeda and ISIL." |16| Saudi-led coalition forces began conducting airstrikes against Houthi-Saleh forces and imposed strict limits on sea and air traffic to Yemen, requiring certification and inspection of shipments as a condition of entry prior to the passage of UNSCR 2216.

From the outset, Saudi leaders sought material and military support from the United States for the campaign, and in March 2015, President Obama authorized "the provision of logistical and intelligence support to GCC-led military operations" and the Obama Administration announced that the United States would establish "a Joint Planning Cell with Saudi Arabia to coordinate U.S. military and intelligence support." U.S. CENTCOM personnel were deployed to provide related support, and U.S. mid-air refueling of coalition aircraft began in April 2015. |17|

In the three years since, the Saudi military and its coalition partners have provided advice and military support to a range of pro-Hadi forces inside Yemen, while waging a persistent air campaign against the Houthis and their allies. Saudi ground forces and special forces have conducted limited cross-border operations, including offensives with coalition partners in some of Yemen's northern and central provinces and operations to retake and move north and west from the southern port city of Aden. A United Nations Verification and Inspection Mechanism (UNVIM) has operated since May 2016 to assist in validating commercial sea and air traffic in support of the arms embargo imposed by Resolution 2216.

Despite concerns over the humanitarian and security ramifications of Saudi-led coalition operations, the Trump Administration has continued the Obama Administration's practice of voicing continuing diplomatic support for Saudi efforts to reinstate the Hadi government. The U.S. government under both presidents has provided ongoing, if limited and variable material, logistical, advisory, and intelligence support to Saudi-led coalition military operations. In response to concerns about civilian casualties resulting from Saudi air strikes, the Obama Administration withdrew U.S. personnel from the joint U.S.-Saudi planning cell in June 2016, and later announced that it would suspend planned sales of precision guided munitions to Saudi Arabia. |18| In 2017, President Trump announced his intention to proceed with the suspended munitions sales and, after a policy review, directed his Administration "to focus on ending the war and avoiding a regional conflict, mitigating the humanitarian crisis, and defending Saudi Arabia's territorial integrity and commerce in the Red Sea." |19| U.S. officials continue to speak in clear terms about what they view as the importance of avoiding civilian casualties and reaching a negotiated solution to the crisis.

In February 2018, the Acting Department of Defense General Counsel wrote to Senate leaders describing the extent of current U.S. support, and reported that "the United States provides the KSA-led coalition defense articles and services, including air-to-air refueling; certain intelligence support; and military advice, including advice regarding compliance with the law of armed conflict and best practices for reducing the risk of civilian casualties." |20| In-flight refueling to the militaries of Saudi Arabia and the United Arab Emirates (UAE) is conducted pursuant to the terms of bilateral Acquisition and Cross Servicing Agreements (ACSAs) between the Department of Defense and the respective ministries of each country. |21| Sales and deliveries of defense articles and services continue pursuant to the Foreign Military Sales and Direct Commercial Sales procedures established in the Arms Export Control Act. The department argues that "the limited military and intelligence support that the United States is providing to the KSA-led coalition does not involve any introduction of U.S. forces into hostilities for purposes of the War Powers Resolution."

Congressional debate over U.S. support to the Saudi-led coalition's military operations since 2015 has reflected reports of Yemeni civilian casualties resulting from the coalition's operations and broader concerns about deteriorating humanitarian conditions, restrictions on the flow of goods and humanitarian aid, the war-driven empowerment of Al Qaeda and Islamic State forces, and Iranian support for the Houthis. Some lawmakers have suggested that U.S. arms sales and military support to the coalition have enabled alleged violations of international humanitarian law, while others have argued that U.S. support to the coalition improves its effectiveness and helps minimize civilian casualties.

Congress has considered but has not enacted proposals to curtail or condition U.S. defense sales to Saudi Arabia or to prohibit the use of funds for coalition support operations. Most recently, on March 20, 2018, the Senate voted to table a motion to discharge the Senate Foreign Relations Committee from further consideration of S.J.Res. 54, a joint resolution that would direct the President to remove U.S. forces from "hostilities in or affecting" Yemen (except for those U.S. forces engaged in counterterrorism operations directed at al Qaeda or associated forces).

Saudi officials acknowledge that some of their operations have inadvertently caused civilian casualties, while maintaining that their military campaign is an act of legitimate self-defense because of their Yemeni adversaries' repeated, deadly cross-border attacks, including ballistic missile attacks. Saudi officials argue that coalition-imposed restrictions and strict inspections of goods and vessels bound for Yemen are required because of Iranian weapons smuggling to Houthi forces. Saudi officials similarly argue that the delivery of goods to ports and territory under Houthi control creates opportunities for Houthi forces to redirect or otherwise exploit shipments for their material or financial benefit. |22|

Figure 4. Houthi Missile Attacks against Saudi Arabia: 2015-2017

Houthi Missile Attacks against Saudi Arabia

Source: Created by PiX, Protected Internet Exchange, April 1 1, 2018.
Note: Missile incidents derived from open source reports. CRS cannot independently verify reports of individual missile launches or claims of missile interceptions and/or impacts.

Yemen's Fragmentation: Conflict in the South

Figure 5. Major General Aidarous al Zubaidi
First Session of the Southern Transitional Council

Major General Aidarous al Zubaidi

Source: Open Source Center, Aden al Ghad (in Arabic), July 5, 2017, Document ID# IMR2017071 132888990.

In Aden, forces allied with President Hadi have repeatedly clashed with southern separatists who have received backing from the United Arab Emirates (UAE), a key member of the Saudi-led coalition. Hadi-UAE tensions are multifaceted, as the sides disagree over how closely to embrace Yemen's main Islamist party (Islah) and how closely to work with southern separatists, many of whom seek either greater southern autonomy or the restoration of an independent state in southern Yemen. In the spring of 2017, the UAE supported General Aidarous al Zubaidi's (see Figure 5) formation of the Southern Transitional Council (STC) after Hadi dismissed him as Aden's governor.

Although President Hadi has relocated Yemen's internationally recognized government to the port city of Aden, the United Arab Emirates (UAE) effectively controls the city through the presence of its own troops or allied tribal militia (known as the Southern Belt or Al Hizam in Arabic). The UAE controls Aden's airport and seaport, and has invested in rebuilding infrastructure. President Hadi's only personally loyal military force in Aden is the Presidential Protection Force, which reportedly is relatively small compared to UAE-allied forces. |23|

After months of periodic clashes between pro-Hadi forces and UAE-backed forces, the STC issued an ultimatum to Hadi threatening to topple his government unless President Hadi dismissed his cabinet and formed a more representative government. On January 30, 2018, the STC seized control of most of Aden from Hadi's troops in just three days. The UAE and Saudi Arabia may have intervened in order to ensure that the STC remains committed to the larger fight against the Houthis. After the fighting subsided, the STC declared that it would remain committed to the coalition's military operations against the Houthis and handed back military installations to Hadi's forces. Nevertheless, it would appear that Hadi has a government in name only and that, on the ground, power resides in the hands of the STC.

The Humanitarian Crisis in Yemen

According to the United Nations Office for the Coordination of Humanitarian Affairs (UN OCHA), out of a total population of nearly 30 million people, 22 million Yemenis are in need of humanitarian assistance, a figure which is 3.4 million people higher than last year. |24| UN OCHA also claims that less than half of all of Yemen's medical facilities are functioning and more than half of all Yemenis lack regular access to safe drinking water. In the education sector, UNICEF has reported that two million Yemeni children are not attending school and 75% of all public school teachers have not been paid their salaries in over a year.

On April 3, the United Nations, Switzerland, and Sweden co-hosted a high-level pledging conference in Geneva to fund the U.N.'s 2018 Humanitarian appeal, which aims to raise $2.96 billion. Donors pledged approximately $2 billon at the conference, $930 million of which came from the combined pledges of Saudi Arabia and the UAE. The United States pledged $87 million and urged "all parties to this conflict to allow unhindered access for all humanitarian and commercial goods through all points of entry into Yemen and throughout the country to reach the Yemenis in desperate need." |25|

Table 1. Pledges for UN 2018 Humanitarian Appeal for Yemen

Country Pledge
Saudi Arabia $500.0 million
United Arab Emirates $500.0 million
Kuwait $250.0 million
United Kingdom $239.7 million
European Commission $132.7 million
United States $87.00 million
UN's Central Emergency Response Fund (CERF) $50.00 million
Germany $40.70 million
Japan $38.80 million
Others (31 pledges) $161.0 million
Source: UN OCHA, April 3, 2018.

Saudi-led Coalition Humanitarian Aid to Yemen

After a Houthi-fired missile with alleged Iranian origins landed deep inside Saudi Arabia in November 2017, the Saudi-led coalition instituted a full blockade of all of Yemen's ports, exacerbating the country's humanitarian crisis. The Trump Administration demanded that the Saudi-led coalition ease the port restrictions, while condemning Iran's reported involvement in missile transfers and launches. |26| On December 20, 2017, the Saudi-led coalition announced that it would end its blockade of Hodeidah port for a 30-day period and permit the delivery of four U.S.-funded cranes to Yemen to increase the port's capability to off-load commercial and humanitarian goods.

As of early March 2018, according to USAID, Hodeidah Port continued to receive commercial and humanitarian shipments despite the mid-February 2018 expiration of the Saudi-led coalition's second 30-day extension of the port opening. |27| Nonetheless, overall imports remain lower than before the coalition closed the port in November 2017. The coalition and UNVIM have recently agreed to increase UNVIM's capacity to inspect cargo coming into Hodeidah (more inspectors and monitors), though there is still a significant backlog of humanitarian supplies waiting to be delivered. |28| According to the World Food Programme, due to low imports and collapsed market systems, food commodity prices continued to increase in February 2018. |29|

Figure 6. Saudi Arabia and UAE Aid to Yemen

Saudi Arabia and UAE Aid to Yemen

Source: Financial Tracking Service of UNOCHA and CRS Graphics

In early 2018, Saudi Arabia unveiled what it calls the Yemen Comprehensive Humanitarian Operations (YCHO), a multi-pronged approach designed to improve humanitarian access and improve Yemen's economy. The main components of YCHO are as follows: |30|

  • Provide $1.5 billion to fund the U.N.'s 2018 Humanitarian appeal (Saudi Arabia and the UAE donated $930 million in March 2018);
  • Deposit $2 billion into the Central Bank in Aden to bolster Yemen's flagging currency (completed in January 2018);
  • Establish 17 safe passage corridors to allow NGOs to deliver humanitarian relief;
  • Improve crane and off-loading capacity at coalition-controlled ports, such as Mocha, Aden, and Mukalla; and
  • Enable up to six flights of C130s per day to the airport in Marib (not controlled by Houthis) to deliver humanitarian supplies.

While Saudi Arabia and the UAE have drawn praise for their combined $930 million donation to the U.N.'s 2018 Humanitarian appeal, |31| humanitarian organizations have charged that the YCHO only targets areas not under Houthi control. Aid advocates assert that commercial shipping access to Hodeidah and the opening of Sana'a airport are necessary to counter the crisis. |32|

U.S. Foreign Aid to Yemen

Since March 2015, the United States has been the largest contributor of humanitarian aid to Yemen. Funds were provided to international aid organizations from USAID's Office of Foreign Disaster Assistance (OFDA), USAID's Food for Peace (FFP), and the U.S. Department of State's Bureau of Population, Refugees, and Migration (State/PRM). The United States has provided a total of $854.223 million in humanitarian assistance in FY2017 and FY2018. |33|

Table 2. U.S. Humanitarian Response to the Complex Crisis in Yemen
(in millions of dollars)

Account FY2011 FY2012 FY2013 FY2014 FY2015 FY2016 FY2017
IDA (USAID/OFDA) 19.946 45.087 61.819 49.858 76.844 81.528 227.996
FFP (UDAID/FFP) 20.013 54.803 50.208 55.000 56.672 196.988 369.629
MRA (State/PRM) 22.500 19.738 18.886 8.900 45.300 48.950 38.125
Total 62.459 119.628 130.913 113.758 178.816 327.466 635.750
Source: Yemen, Complex Emergency–USAID Factsheets.

Table 3. U.S. Bilateral Aid to Yemen: FY2016-FY2017
(in millions of dollars)

Account FY2016 FY2017
Economic Support Fund 29.300 14.700
Development Assistance - 25.000
Global Health 5.000 -
Total 34.300 39.700
Source: USAID

U.S. Counterterrorism Operations in Yemen

As the Saudi-led coalition's campaign against the Houthis continues and Yemen fragments, the United States not only has sustained counterterrorism operations against Al Qaeda in the Arabian Peninsula (AQAP) and various affiliates of the Islamic State, but it has markedly increased the tempo of strikes. According to one source, in 2017, the United States launched more than 120 strikes in Yemen, which was more than in the previous four years combined. |34| Repeated U.S. strikes have degraded, but not defeated, groups such as AQAP. According to a spokesperson for U.S. Central Command (CENTCOM), attacks "have put pressure on A.Q.A.P.'s network, severely limiting their freedom of movement, disrupting the organization's ability to recruit and train, and limiting A.Q.A.P.'s ability to plan and execute external operations." |35| In a December 2017 war powers resolution letter to Congress on the deployments of United States Armed Forces equipped for combat, the President reported:

A small number of United States military personnel are deployed to Yemen to conduct operations against al-Qa'ida in the Arabian Peninsula (AQAP) and ISIS. The United States military continues to work closely with the Government of Yemen and regional partner forces to dismantle and ultimately eliminate the terrorist threat posed by those groups. Since the last periodic update report, United States forces have conducted a number of airstrikes against AQAP operatives and facilities in Yemen, and supported the United Arab Emirates- and Yemen-led operations to clear AQAP from Shabwah Governorate. In October, United States forces also conducted airstrikes against ISIS targets in Yemen for the first time. United States forces, in a non-combat role, have also continued to provide logistics and other support to regional forces combatting the Houthi insurgency in Yemen. |36|

Figure 7. U.S. Air Strikes in Yemen

U.S. Air Strikes in Yemen

Source: Long War Journal, Foundation for the Defense of Democracies, 2017: A record year for US counterterrorism strikes, January 3, 2018|
Notes: According to the source, "Air strike data has been obtained from press reports from the respective local outlets, US military reports, wire reports (AFP, Reuters, etc.), as well as independent reporting from FDD's Long War Journal."

Where is the Yemen Conflict Heading?

Yemen is a failed state. No single force is in control and many local actors wield political power. Even before the reemergence of conflict in 2015, Yemen was already in the throes of a humanitarian crisis and facing terrorist violence, acute water shortages, and rampant corruption. The war has exacerbated all of Yemen's longstanding problems, and the U.S. intelligence community believes that conflict is likely to continue during 2018. |37|

Despite these dire prospects, U.S. policymakers have been calling for a political solution to the conflict based on several factors. The war creates a pretext for transnational Sunni Salafi-Jihadi terrorist groups like Al Qaeda in the Arabian Peninsula and the Islamic State to recruit fighters to fight the Houthis, who these groups consider heretical. The war arguably also continues to allow Iran to meddle beyond its borders and transfer weapons and knowledge to Houthi forces, thereby increasing their capabilities

The war has made Yemen one of the world's worst humanitarian crises. Like the U.S. Congress, lawmakers in Canada and several European countries also have vigorously debated the merits of continuing to support the Saudi-led coalition's ongoing military campaign. |38| Finally, the war has the potential to affect forces far beyond Yemen's borders. If the Houthis are able to successfully target oil facilities in Saudi Arabia and the Bab al Mandab strait, world energy markets could react negatively, driving up global oil prices.

While Yemen has fragmented into many different power centers, there are still two primary combatants in the conflict, the Saudi-led coalition and Houthi forces. The latter appear determined to fight indefinitely. Therefore, the duration of the conflict seems to rest primarily in the hands of Saudi Arabia and the United Arab Emirates. The coalition has deployed a limited number of ground forces in the north to assist local Yemeni allies in retaking territory, but primarily continues to rely on air power. |39| While the air campaign has caused significant damage to northern Yemen, Saudi Arabia has not suffered significant casualties. Nor has its leadership suffered any significant public backlash, despite continued Houthi incursions along its southern border and Houthi missile attacks inside the kingdom.

The coalition could attempt to rebuild a new Yemeni government-controlled military, but that assumes that the coalition itself is united in purpose. It would appear that fissures (ideological, religious, tribal, and regional) between Saudi-backed and UAE-backed local forces have hindered coalition military progress to date. |40| Likewise, Houthi forces also have fissures between the political and military wings of the movement. |41|

For the international community, one of the biggest obstacles to resolving the conflict is that Saudi Arabia strongly endorses continued adherence to UNSCR 2216, which the Houthis regard as biased against them. |42| Some humanitarian advocates have called for a new Security Council resolution on the Yemen conflict. |43| Beyond the United Nations, Oman has attempted to serve as a neutral third party that could facilitate negotiations. In February 2018, Oman agreed to host a new round of peace talks, though no date for talks has been set. In March 2018, U.S. Defense Secretary James Mattis traveled to Oman to meet with Sultan Qaboos, noting that the Omanis "have been on the record that they want to see this civil war stopped for obvious reasons." |44|

Overall, U.S. policymakers continue to balance national security interests with concern for the humanitarian dimensions of the Yemen conflict. For the Trump Administration, officials have condemned Iranian interference in Yemen while calling on the Saudi-led coalition to maintain humanitarian access to Yemen. While U.S. officials have supported the continued defense of Saudi Arabia against Houthi missile and rocket strikes, they also have openly called on coalition members to use air power judiciously to minimize civilian casualties. In the meantime, as the Saudi-led coalition's campaign against the Houthis continues, and Yemen fragments, the United States not only has sustained counterterrorism operations against Al Qaeda in the Arabian Peninsula (AQAP) and various affiliates of the Islamic State, but it has markedly increased the tempo of strikes.

The United States has few good choices in Yemen. If the United States becomes more directly involved in brokering a political solution to the conflict outside the bounds of UNSCR 2216, it risks alienating the leaders of the coalition, Saudi Arabia and the United Arab Emirates, while also boosting Iran's legitimacy. If the war continues indefinitely, the humanitarian situation worsens, while the risk of regional spillover increases. For the foreseeable future, policymakers and Congress face these competing U.S. interests as they assess options for responding to the war in Yemen.

Jeremy M. Sharp is a Specialist in Middle Eastern Affairs.

[Source: By Jeremy M. Sharp, Congressional Research Service, R43960, Washington D.C., 12Apr18]


1. The Houthi movement (also known as Ansar Allah or Partisans of God) is a predominantly Zaydi Shiite revivalist political and insurgent movement. Yemen's Zaydis take their name from their fifth Imam, Zayd ibn Ali, grandson of Husayn. Zayd revolted against the Umayyad Caliphate in 740, believing it to be corrupt, and to this day, Zaydis believe that their imam (ruler of the community) should be both a descendent of Ali (the cousin and son-in-law of the prophet Muhammad) and one who makes it his religious duty to rebel against unjust rulers and corruption. A Zaydi state (or Imamate) was founded in northern Yemen in 893 and lasted in various forms until the republican revolution of 1962. Yemen's modern imams kept their state in the Yemeni highlands in extreme isolation, as foreign visitors required the ruler's permission to enter the kingdom. Although Zaydism is an offshoot of Shia Islam, its legal traditions and religious practices are similar to Sunni Islam. Moreover, it is doctrinally distinct from "Twelver Shiism," the dominant branch of Shi'a Islam in Iran and Lebanon. The Houthi movement was formed in the northern Yemeni province of Sa'da in 2004 under the leadership of members of the Houthi family. It originally sought an end to what it viewed as efforts to marginalize Zaydi communities and beliefs, but its goals grew in scope and ambition in the wake of the 2011 uprising and government collapse to embrace a broader populist, antiestablishment message. Skeptics highlight the movement's ideological roots, its alleged cooperation with Iran, and the slogans prominently displayed on its banners: "God is great! Death to America! Death to Israel! Curse the Jews! Victory to Islam!" [Back]

2. Available online at: [] [Back]

3. After the attack, the White House issued a statement noting U.S. concern "about the Houthis' latest attempt to escalate the war in Yemen, this time by attacking a commercial vessel while it transited one of the world's busiest shipping lanes, the Bab al-Mandab, in international waters." See, White House, "Statement by the Press Secretary on the Houthi Commercial Maritime Attack," April 4, 2018. [Back]

4. In February 2018, the U.N. Office of the High Commissioner for Human Rights reported that "Since March 2015 and as of 8 February, the UN Human Rights office had documented 15,467 civilian casualties, with 5,974 killed and 9,493 injured." See, "Civilians in war-torn Yemen 'under fire on all sides' - UN Rights Chief," UN News, February 12, 2018. [Back]

5. On April 14, 2015, the United Nations Security Council adopted Resolution 2216, which imposed sanctions on individuals undermining the stability of Yemen and authorized an arms embargo against the Houthi-Saleh forces. It also demanded that the Houthis withdraw from all areas seized during the current conflict, relinquish arms seized from military and security institutions, cease all actions falling exclusively within the authority of the legitimate Government of Yemen, and fully implement previous council resolutions. [Back]

6. United Nations Panel of Experts on Yemen, Letter dated 26 January 2018 from the Panel of Experts on Yemen mandated by Security Council resolution 2342 (2017) addressed to the President of the Security Council. [Back]

7. "UN Yemen Envoy: Houthis Scrapped Peace Deal at last Minute," Middle East Eye, February 27, 2018. [Back]

8. United Nations Security Council, 8205th Meeting, SC/13250, Amid Deteriorating Conditions in Yemen, Security Council Presidential Statement Calls for Humanitarian Access, Strict Adherence to Embargo, March 15, 2018. [Back]

9. op.cit., United Nations Panel of Experts on Yemen. [Back]

10. According to the U.S. intelligence community, "Iran's support to the Houthis further escalates the conflict and poses a serious threat to US partners and interests in the region. Iran continues to provide support that enables Houthi attacks against shipping near the Bab al Mandeb Strait and land-based targets deep inside Saudi Arabia and the UAE." See, Office of the Director for National Intelligence, Testimony Prepared for Hearings on Worldwide Threats, February 2018. [Back]

11. For example, see: "Report: Bombs disguised as Rocks in Yemen show Iranian Aid," Associated Press, March 26, 2018; "Iran Steps up Support for Houthis in Yemen's War - Sources," Reuters, March 21, 2017; "Maritime Interdictions of Weapon Supplies to Somalia and Yemen: Deciphering a Link to Iran," Conflict Armament Research, November 2016; "U.S. Officials: Iran Supplying Weapons to Yemen's Houthi Rebels," NBC News, October 27, 2016; "Exclusive: Iran steps up Weapons Supply to Yemen's Houthis via Oman–Officials," Reuters, October 20, 2016; "Weapons Bound for Yemen Seized on Iran Boat: Coalition," Reuters, September 30, 2015; and "Elite Iranian guards training Yemen's Houthis: U.S. officials," Reuters, March 27, 2015. [Back]

12. "The Houthi Hezbollah: Iran's Train-and-Equip Program in Sanaa," Foreign Affairs, March 31, 2016. [Back]

13. United States Mission to the United Nations, Press Release: "Ambassador Haley on Weapons of Iranian Origin Used in Attack on Saudi Arabia," November 7, 2017. [Back]

14. House Armed Services Committee Hearing on Terrorism and Iran, Full Transcript, February 27, 2018. [Back]

15. Prepared by Christopher Blanchard, Specialist in Middle Eastern Affairs. [Back]

16. President Hadi correspondence with GCC governments printed in U.N. Document S/2015/217, "Identical letters dated 26 March 2015 from the Permanent Representative of Qatar to the United Nations addressed to the Secretary-General and the President of Security Council," March 27, 2015. [Back]

17. Refueling operations began April 7, 2015 according to Department of Defense spokesman Col. Steve Warren. See Andrew Tilghman, "U.S. launches aerial refueling mission in Yemen," Military Times, April 8, 2015. [Back]

18. Reuters, "U.S. withdraws staff from Saudi Arabia dedicated to Yemen planning," August 19, 2016. [Back]

19. Letter from Department of Defense Acting General Counsel William Castle to Senators Mitch McConnell and Chuck Schumer, February 27, 2018. [Back]

20. Ibid. [Back]

21. ACSA agreements are governed by 10 USC 2341-2350. The agreements provide for reciprocal logistical support under a variety of circumstances, and their underlying statutory authority does not prohibit U.S. support to partner forces engaged in armed conflict. U.S. ACSA agreements with Saudi Arabia and the UAE provide for the transfer of support to third parties with the prior written consent of both the original provider and original recipient. The U.S. agreement with Saudi Arabia was signed in May 2016. The executive branch has not publicly specified what legal authority or agreement provided for refueling support to Saudi aircraft from March 2015 through May 2016. [Back]

22. Saudi Press Agency, Command of the Coalition to Restore Legitimacy in Yemen Issues Statement, November 22, 2017. [Back]

23. "UAE runs Aden as Protectorate, while Hadi hides in the Shadows," Middle East Eye, November 27, 2017. [Back]

24. Yemen Humanitarian Update, Covering 26 March - 03 April 2018 | Issue 9. [Back]

25. U.S. State Department, "United States Announces Additional Humanitarian Assistance for Yemen at High-Level Pledging Conference," Office of the Spokesperson, Washington, DC, April 3, 2018. [Back]

26. The White House, Office of the Press Secretary, Statement by President Donald J. Trump on Yemen, December 06, 2017. Other statements include: The White House, Office of the Press Secretary, White House Statement on Iranian-Supported Missile Attacks Against Saudi Arabia, November 8, 2017; The White House, Office of the Press Secretary, Statement from the Press Secretary on the Humanitarian Crisis in Yemen, November 24, 2017; The White House, Office of the Press Secretary, Statement by the Press Secretary Regarding the Violence and Humanitarian Conditions in Yemen, December 08, 2017. [Back]

27. USAID, Yemen - Complex Emergency Fact Sheet #5, Fiscal Year 2018, March 9, 2018. [Back]

28. "U.N. quietly steps up Inspection of Aid Ships to Yemen," Reuters, April 5, 2018. [Back]

29. USAID, Yemen - Complex Emergency Fact Sheet #6, Fiscal Year 2018, April 3, 2018. [Back]

30. See, Yemen Comprehensive Humanitarian Operations (YCHO): Unprecedented Relief to the People of Yemen. Available online at: [] [Back]

31. "Saudis, UAE draw praise for pledging aid to Yemen," Associated Press, April 3, 2018. [Back]

32. "Amid criticism, U.S. still supporting Saudis in Yemen," Washington Post, March 21, 2018. [Back]

33. Op. cit., USAID, April 3, 2018. [Back]

34. "2017: A Record Year for US Counterterrorism Strikes," Long War Journal, Foundation for the Defense of Democracies, January 3, 2018. See also, U.S. Department of Defense, CENTCOM Officials Provide Update on Recent Counterterrorism Strikes in Yemen, Dec. 20, 2017. [Back]

35. "The U.S. Has Pummeled Al Qaeda in Yemen. But the Threat Is Barely Dented," New York Times, December 30, 2017. [Back]

36. Text of a Letter from the President to the Speaker of the House of Representatives and the President Pro Tempore of the Senate, December 11, 2017. [Back]

37. The U.S. intelligence community reported to Congress in February 2018 that Yemen's conflict is "likely to continue for the foreseeable future," and "continued fighting almost certainly will worsen the vast humanitarian crisis." Office of the Director for National Intelligence, Testimony Prepared for Hearings on Worldwide Threats, February 2018. [Back]

38. "Europeans Cut Saudi Arms Sales," Arms Control Today, March 2018. [Back]

39. Jane's Sentinel Security Assessment - The Gulf States, Army - Saudi Arabia, April 5, 2018. [Back]

40. For examples, see "Yemen's Southern Powder Keg," Chatham House, March 2018. [Back]

41. "Saudi and Houthi Willingness to start Peace Talks reflects both sides' need to end war in Yemen," Jane's Intelligence Weekly, February 16, 2018. [Back]

42. "How a tough UN Resolution is making Push for Yemen Peace Talks Harder," Christian Science Monitor, April 9, 2018. [Back]

43. "The Conflict in Yemen: Time for a New Approach," International Rescue Committee, April 5, 2018. [Back]

44. "Mattis to discuss arms smuggling into Yemen on Oman trip," The National, March 12, 2018. [Back]

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