Non-international armed conflicts in Yemen

Multiple parallel and overlapping non-international armed conflicts are taking place in Yemen.

• First, the longstanding non-international armed conflict between the government and the Houthis continues. During 2015, the Houthis assumed control over Yemen’s capital Sana’a. Upon invitation of Yemen’s President Hadi, an international coalition led by Saudi Arabia intervening since March 2015. The involvement of Saudi Arabia and its allies does not affect the classification as it takes place with the consent of Yemen.
• Second, the government is also involved in a non-international armed conflict with al-Qaeda in the Arabian Peninsula. With the apparent consent or cooperation of the Yemen government, the United States has been undertaking targeted operations against al-Qaeda in the Arabian Peninsula. However, this does not affect the classification of the conflict.
• Third, armed groups, including the Houthis and al-Qaeda in the Arabian Peninsula are also fighting each other.
• Finally, the establishment of Southern Transitional Council, in 2017, has led to the surfacing of historical fault lines in Yemen. This resulted in the outbreak of a non-international armed conflict breaking out between the government and the STC

In addition to the long-standing armed conflict opposing the Houthis to the government, new conflicts have emerged over the past years.

Two criteria need to be assessed in order to answer the question whether a situation of armed violence amounts to a non-international armed conflict.

• First, the level of armed violence must reach a certain degree of intensity that goes beyond internal disturbances and tensions.
• Second, in every non-international armed conflict, at least one side to the conflict must be a non-state armed group which must exhibit a certain level of organization in order to qualify as a party to the non-international armed conflict. Government forces are presumed to satisfy the criteria of organization. For further information, see 'non-international armed conflict' in our classification section.

Internsity of violence

Various indicative factors are used to assess whether a given situation has met the required intensity threshold, such as the number, duration, and intensity of individual confrontations; the types of weapons and military equipment used; the number of persons and types of forces participating in the fighting; the number of casualties; the extent of material destruction; the number of civilians fleeing; and the involvement of the United Nations Security Council. For further information, see 'non-international armed conflict - intensity of violence' in our classification section.

Yemeni Government v. the Houthis

From January 2011 onwards, against the background of the Arab spring, peaceful protests started to spread across the country to request the resignation of then President Saleh. The Houthis and tribal leaders supported the protests. After dozens of protestors were reportedly killed and many more injured during a demonstration in Sana’a on 18 March 2011, President Saleh declared a state of emergency. Sari Arraf, ‘The Armed Conflict in Yemen: A Complicated Mosaic’, Geneva Academy, October 2017, p. 2. The violence further escalated towards the end of May, when fierce fighting erupted between forces loyal to the President and tribal forces. Artillery caused heavy damage and thousands fled the city. Both sides reportedly used weapons such as AK-47 automatic rifles, sniper rifles, machine guns, rocket-propelled grenades and mortars. In addition, airstrikes were also carried out by the Yemeni Air Force and the Yemeni Navy against armed groups around the capital and in the south. The escalating violence was not limited to the capital: Houthis took advantage of the chaos in Yemen to seize more territory in the north, in particular by taking full control over Saada province. Christoph Wilcke, ‘Disappearances and arbitrary arrests in the armed conflict with Huthi rebels in Yemen’, HRW, 24 October 2008.

Armed clashes continued during the summer in various parts of Yemen. After expressing concern over the worsening humanitarian situations in Yemen in June, August, and September 2011, the Security Council adopted Resolution 2014 (2011) in October 2011 to call on all parties to sign the transition initiative brokered by the Gulf Cooperation Council (GCC). While Saleh signed the agreement proposed by the GCC to step down from power and to transfer power to Abdrabbo Mansour Hadi on 23 November 2011, the Houthis felt marginalized and ignored. They have taken advantage of the chaos in Yemen to continue fighting with government forces and tribal groups in northern Yemen and systematically expand their control. This resulted in September 2014 in the seizure of Yemen’s capital Sana’a, supported by some of Saleh’s allies. Afterwards, the Houthis expanded their control south to Ibb province and west to al-Hudayda. See Stuart Casey-Maslen (ed), The War Report 2012, Oxford University Press, 2013, p 188.; Stuart Casey-Maslen (ed), The War Report 2013, Oxford Universtiy Press, 2014 and A. Bellal (ed), The War Report 2014, Oxford University Press, 2015, p 240 ff.

The takeover of Sana’a followed a new wave of protests demanding for a new government and the implementation of the transition accord. However, the Houthis took advantage of the situation of instability in Yemen to expand their power. Another important factor that helped them was their alignment with several local tribes and government forces loyal to former President Saleh, driven by the existence of a common enemy. The political situation in the capital remained very unstable. A UN-brokered peace agreement with the Houthis – the Peace and National Partnership Agreement (PNPA) – was concluded. While the agreement envisaged that the Houthis would have been included in the government, it was never implemented and tensions between the Houthis and President Hadi re-emerged in Sana’a. Hadi was placed under house arrest and later fled to Aden on 21 February 2015. On 19 March 2015, the situation of violence reached a new peak when fighting broke out between military units loyal to Saleh and Hadi's forces in Aden. Consequently, President Hadi fled the country and sought refuge in Saudi Arabia, where he asked for help. Accordingly, a Saudi-led coalition intervened on the side of the Yemeni government in 2015. ‘Houthis push into Yemeni capital amid rallies’, Al Jazeera, 20 August 2014; ‘Yemen: Houthi Rebels and Militia Clash in Sanaa’, BBC, 19 September 2014; M. Ghobari, ‘Houthis Tighten Grip on Yemen Capital After Swift Capture, Power-Sharing Deal’, Reuters, 22 September 2014; April Longley Alley, ‘Yemen’s Houthi takeover’, International Crisis Group, 22 December 2014; ‘Yemen President Quits Amid Worsening Crisis’, Al Jazeera, 22 January 2015;  Mohamed Ghobari and Mohammed Mukhashaf, ‘Yemen’s Hadi Flees to Aden and Says he is Still President’, Reuters, 21 February 2015; Sari Arraf, ‘The Armed Conflict in Yemen: A Complicated Mosaic’, Geneva Academy, October 2017, p. 3-5; ‘Soldiers loyal to Yemen's former president storm Aden airport’, The Guardian, 19 March 2015; ‘UN-led Talks on Yemen to Begin in Doha as Saudi Arabia Backs Hadi’, Middle East Eye, 24 March 2015; ‘Yemen war: 5 years since the Houthis’ Sanaa takeover’, Al Jazeera, 21 September 2019.

Since the intervention of the coalition took place at the request of the internationally recognised government, and the classification of the conflict does not change. This means that the coalition becomes a party to the pre-existing NIAC between the Yemeni Government and the Houthis.

The coalition immediately launched an air offensive to counter the Houthis' territorial expansion. This offensive was met with fierce resistance. Mohammed Mukhashaf, ‘Yemen’s Houthis Seize Central Aden District, Presidential Site’, Reuters, 3 April 2015. The escalation of the situation led the UN Security Council to adopt Resolution 2216, which confirmed support for Hadi's government and called on the Houthis to withdraw from the areas they had seized. S/Res/2216 (2015), 14 April 2015. The coalition's main objective was, with support of Southern Resistance forces, to retake Aden from the Houthis. After an intense battle, they succeeded on 17 July 2015. Throughout 2015, the coalition conducted multiple campaigns of airstrikes across the country, reportedly including the use of cluster munitions. For example on 12 May an airstrike on a market and neighboring lemon grove in Zabid, south of Hodaida, killed at least 60 civilians, an airstrike conducted on 4 July on a village market in Muthalith Ahim killed over 65 people and on 24 July an airstrike on homes in the port city of Mokha killed at least 65 civilians. Human Rights Watch, ‘World report 2016: Events of 2015’, Bristol University Press, 2016, p. 643-645; Michael Knights and Alex Almeida, ‘The Saudi–UAE War Effort in Yemen (Part 1): Operation Golden Arrow in Aden’, The Washington Institute, 10 August 2015.

Since then, fighting has continued between the Yemeni government, supported by the coalition, and the Houthis. More than 150,000 people are reported to have been killed between the coalition's intervention in March 2015 and June 2019. This indicates the continuing nature of the conflict. Of those 150,000, nearly 15,000 civilians were killed in attacks directly targeting civilian gatherings or buildings. Furthermore, reports indicate that nearly 9,000 (60%), from over 7,000 separate incidents, were caused by air strikes by the Saudi-led coalition. Moreover, since the start of the coalition’s airstrike campaign, over 24,600 airstrikes were carried out. Matthias Sulz and Sam Jones, ‘Over 100,000 reported killed in Yemen war’, ACLED Data, 31 October 2019; ‘The war on Yemen’s civilians’, Campaign Against Arms Trade, 15 February 2022; Global Conflict Tracker, ‘War in Yemen’, Council on Foreign Relations, 4 May 2022.

By the end of 2021, beginning of 2022, the fighting has escalated between the Houthis and the Saudi-led coalition. In the context of their attempt to capture Marib, the Houthis have carried out direct attacks on Saudi Arabia and, for the first time, on the UAE. In response, the coalition conducted airstrikes on Yemen leading to a record number of civilians casualties in January 2022, according to Hans Grundberg, Special Envoy of the UN Secretary-General for Yemen. One of these airstrikes hit a Houthi-run detention facility, killing 91 detainees and injuring 236 people. Michael Georgy and Peter Graff, ‘Explainer: Why Yemen is at war’, Reuters, 25 January 2022; Federica Marsi, ‘Yemen civilians bear the brunt of escalating Houthi-UAE conflict’, Al Jazeera, 27 January 2022; ‘Saudi-led coalition says it’s probing deadly prison strike’, AP News, 27 January 2022; Giorgio Cafiero, ‘Yemen: Intensifying war worsens world’s worst civilian crisis’, Al Jazeera, 7 February 2022; Lisa Schlein, ‘UN Calls for Saudi Probe of Airstrikes on Yemen Detention Facility to be Independent, Transparent’, VOA News, 29 January 2022; UN, ‘Sharp escalation in fighting across Yemen risks spiralling out of control’, UN News, 15 February 2022; Nabil Hetari, ‘A new phase in the Yemen war: context and consequences’, Washington Institute, 28 February 2022.

On 1 April 2022, the warring parties to Yemen’s conflict agreed to a two month ceasefire agreement, starting with the Muslim holy month of Ramadan. UN special envoy Hans Grundberg explained that the truce could have been renewed with the agreement of the parties. He also added that ‘The parties accepted to halt all offensive military air, ground and maritime operations inside Yemen and across its borders; they also agreed for fuel ships to enter into Hodeidah ports and commercial flights to operate in and out of Sanaa airport to predetermined destinations in the region.’ ‘Yemen’s warring parties agree to two-month truce, UN says’, Al Jazeera, 1 April 2022. On 3 October 2022, the parties to the agreement failed to consent to its renewal. While the government has blamed the Houthi rebels for the end of the agreement, the opposition forces refused to comment. ‘Yemen’s warring sides fail to agree extension to UN-backed truce’, Al Jazeera, 3 October 2022.

On account of the frequency of armed attacks and armed confrontations, the number of casualties, the number of people forced to flee ongoing hostilities, and the types of weapons and military equipment utilized, it is possible to conclude that there is a non-international conflict between the Yemeni government and the Houthis.

Houthis v. Al-Qaeda in the Arabian Peninsula

Al Qaeda in the Arabian Peninsula (AQAP) took advantage of the security vacuum during the 2011 uprising to seize power in and around several cities in southern Yemen. In the period 2011-2012, this resulted in several small Islamic emirates being declared by AQAP. Peter Salisbury, ‘Yemen: Stemming the Rise of a Chaos State’, Chatham House, 25 May 2016, p 3; ‘Yemen’s al-Qaeda: Expanding the Base’, International Crisis Group, 2 February 2017, p 6; Sari Arraf, ‘The Armed Conflict in Yemen: A Complicated Mosaic’, Geneva Academy, October 2017, p 9; Andrea Carboni and Matthias Sulz, ‘The wartime transformation of AQAP in Yemen’, ACLED Data, 14 December 2020.

AQAP took advantage of the situation to declare war against the Houthis, who adhere to a fundamentally different form of Islam. Notably, when the Houthis started their campaign towards southern Yemen, AQAP began to carry out numerous attacks against the Houthis. This reportedly resulted in 149 attacks between late September 2014 and mid-December 2014. The fighting between the two sides took place mainly in the mountains of Al Bayda, where the Houthis took the upper hand, as well as in Taiz and Marib. Oren Adaki, ‘AQAP, Houthis clash in central Yemen’, The Long War Journal, 16 October 2014; Oren Adaki, ‘AQAP claims 149 attacks in Yemen since late September’, The Long War Journal, 19 December 2014; ‘Yemen’s al-Qaeda: Expanding the Base’, International Crisis Group, 2 February 2017, p 8; Andrea Carboni and Matthias Sulz, ‘The wartime transformation of AQAP in Yemen’, ACLED Data, 14 December 2020. During the following years, confrontations between the two sides continued, with AQAP trying to secure territory in southern Yemen and the Houthis trying to seize power in southern Yemen. Andrea Carboni and Matthias Sulz, ‘The wartime transformation of AQAP in Yemen’, ACLED Data, 14 December 2020; Elisabeth Kendall, ‘Where is AQAP now?’, Sana’a Center For Strategic Studies, 21 October 2021.

Enmity between AQAP and other Islamist groups has greatly weakened AQAP and caused a decrease in their activities. The number of engagements has roughly halved compared to the 2015-2017 period, when they were fiercely resisting the Houthis. In 2018 and 2019, they have focused on IS and other Islamist groups. This has weakened them to such an extent that they have adjusted their strategy and are pushing back as an anti-Houthi movement. Despite the number of engagements dropping, proportionately the focus has clearly returned to fighting the Houthis. Although greatly reduced, confrontations between the two sides continue to take place. Andrea Carboni and Matthias Sulz, ‘The wartime transformation of AQAP in Yemen’, ACLED Data, 14 December 2020; Elisabeth Kendall, ‘Where is AQAP now?’, Sana’a Center For Strategic Studies, 21 October 2021.

On account of the frequency of armed attacks and armed confrontations, the number of casualties, the number of people forced to flee ongoing hostilities, and the types of weapons and military equipment utilized, the required degree of intensity has been reached since September 2014. The fighting has continued and hence there is a non-international conflict between the Houthis and Al Qaeda in the Arabian Peninsula.

Yemeni Government v. Al Qaeda in the Arabian Peninsula

During the 2011 uprising, AQAP reorganized in order to take advantage of the vacuum in Yemen. They created Ansar al-Sharia (AAS, “Supporters of Islamic Law”) to gain a foothold in Yemen itself and distinguish their international terrorist activities from domestic objectives. This enabled them to assume control over several towns in the south of Yemen, such as Zinjibar, the capital of Abyan Governorate. ‘Yemen’s al-Qaeda: Expanding the Base’, International Crisis Group, 2 February 2017, pp. 6-7. This was accompanied by an outbreak of armed violence in the south of Yemen between a combination of Yemeni security services and local militias (kown as Popular Committees) on the one hand, and AAS fighters on the other hand. The situation escalated and the confrontations continued. Louise Arimatsu and Mohbuba Choudhury (eds), The Legal Classification of the Armed Conflicts in Syria, Yemen and Libya, Chatham House, 2014, p 29; Nadwa Al-Dawsari, ‘The Popular Committees of Abyan, Yemen: A necessary evil or an opportunity for security reform’, MEI, 5 March 2014.

After President Saleh signed the transition initiative, President Hadi was elected in February 2012. Following his inauguration, AQAP intensified its attacks on government targets. For example, on 21 May 2012, a suicide bomber attacked a military parade in Sana’a killing 96 members of the Government’s armed forces and wounding over 200 people. Mohammed Ghobari and Tom Finn, ‘Suicide bomber kills 90 in Yemen, al Qaeda vows more attacks’, Reuters, 21 May 2012; S. Haddad, ‘Yemen’, in Louise Arimatsu and Mohbuba Choudhury (eds), The Legal Classification of the Armed Conflicts in Syria, Yemen and Libya, Chatham House, 2014, pp 24-25. As a reaction, airstrikes were carried out by the Yemeni Air Force and the Yemeni Navy against AQAP in the south. Moreover, in May 2012, when the Government-linked forces ousted AQAP from Abyan, ‘Yemen’s al-Qaeda: Expanding the Base’, International Crisis Group, 2 February 2017, p 7.

The levels of armed violence remained significant throughout 2012, 2013, and 2014, in particular in the south where the government attempted to drive out AQAP. The escalation of the situation led the UN Security Council to adopt Resolution 2216, which condemned the growing number of AQAP attacks in Yemen. UNSC Res 2216, 14 April 2015.

AQAP, when it suited them, joined the larger structure of a common anti-Houthi front. In this way, they took advantage of the fact that the fighting was largely concentrated against the Houthis to seize control over different governorates and cities. For instance, only a week after the Saudi-led coalition began attacking Huthi-Saleh forces from the air in 2015, AQAP moved into the eastern governorate of Hadramout. They seized the provincial capital, Mukalla, without resistance. AQAP remained in power for over a year, as the coalition was fighting the Houthis elsewhere. In April 2016, AQAP was driven out of Mukalla by the Government-aligned forces. Despite this loss of territory, AQAP was still able to carry out deadly attacks against Government-related targets and to hold certain territories in the governorates of Hadhramaut, Shabwa and Abyan. ‘Yemen conflict: Troops retake Mukalla from al-Qaeda’, BBC News, 25 April 2016; ‘Yemen’s al-Qaeda: Expanding the Base’, International Crisis Group, 2 February 2017, p 9; Sari Arraf, ‘The Armed Conflict in Yemen: A Complicated Mosaic’, Geneva Academy, October 2017, p 6; Andrea Carboni and Matthias Sulz, ‘The wartime transformation of AQAP in Yemen’, ACLED Data, 14 December 2020.

As discussed earlier, AQAP has been weakened in recent years, leading to a reduction in its activities. Nevertheless, they remain involved in hostilities with the Yemeni government on a smaller scale. For instance, it was reported that AQAP carried out attacks in Al Bayda and Shabwah in June 2021. Although there have been no recent reports of activities between the two sides, given the unstable situation in Yemen, it is premature to conclude a declassification of the NIAC between the Yemeni Government and AQAP. Ameneh Mehvar, Fanan Bilal, Tarek Albaik and Emile Roy, ‘Regional overview: Middle East 12-18 June’, ACLED Data, 23 June 2021.

On account of the frequency of armed attacks and armed confrontations, the number of casualties, the number of people forced to flee ongoing hostilities, and the types of weapons and military equipment utilized, the required degree of intensity has been reached since March 2011. The fighting has continued, although AQAP seems to have recently entered a phase of retrenchment in which they are less active, and hence there is a non-international conflict between the Yemeni Government and Al Qaeda in the Arabian Peninsula.

Yemeni Government v. the Southern Transitional Council

The Southern Transitional Council (STC) was established in May 2017 by Aydrous al-Zubaidi. The STC seeks independence for southern Yemen, as it existed before the unification of Yemen. The Houthi/Saleh alliance being a common enemy, the Hadi Government and pro-independence fighters have fought on each other's side. However, significant ideological differences between them increasingly emerged and this gave rise to the formal emergence of the STC. From May 2017, tensions between the two sides began to increase, with multiple rallies and counter-rallies. In January 2018, this culminated in a direct confrontation between STC forces and Hadi loyalists in Aden. These clashes resulted in dozens of people killed. On 30 January, the STC reportedly took control over Aden. Nevertheless, tensions remained and resulted in regular clashes between STC forces and Hadi Government forces in Aden and in al-Dhale and Taiz governorates. On 7 August, Prime Minister Hadi's guards reportedly fired on people in Aden, to which the STC responded with an offensive the same day. More than 40 people were killed. In this offensive, STC forces seized control over government military bases in Zinjibar and al-Kawad.  The government launched counter-attacks and recaptured bases in the Shebwa Governorate and also regained control of Zinjibar. In addition, on 28 August, government forces advanced into Aden, leading to clashes in the eastern part. Mohammed Mukashaf, ‘Clashes erupt in Yemen’s Aden, three dead’, Reuters, 7 August 2019; ‘Yemeni separatists extend control in south, Saudi-led forces strike capital’, Reuters, 19 August 2019; International Crisis Group, Crisis Watch – Iraq, July 2019; ‘Yemeni government forces take control of Ataq after clashes’, Al Jazeera, 23 August 2019; International Crisis Group, Crisis Watch – Iraq, September – August 2019.

Clashes between the two sides continued until Saudi Arabia mediated the Riyadh Agreement on 5 November 2019, which would bring an end to the fighting. Nevertheless, some minor clashes erupted in January 2020, indicating that tensions between the STC and the Yemeni government had not yet subsided. Fatima Abo Alasrar, ‘Will reviving the Riyadh Agreement quell conflict in South Yemen?’, The Arab Gulf States Institute in Washington, 10 August 2020; International Crisis Group, Crisis Watch – Iraq, September – October 2019 and January 2020. Throughout 2020, tensions continued to be present, which from time to time escalated into confrontations and then temporarily de-escalated again. The same evolution occurred in 2021 and continues to this day. Emile Roy, ‘Diplomatic efforts fail to subdue the conflict’, ACLED Data, 2021; International Crisis Group, Crisis Watch – Iraq, February 2020 – April 2022.

On account of the frequency of armed attacks and armed confrontations, the number of casualties, the number of people forced to flee ongoing hostilities, and the types of weapons and military equipment utilized, the required degree of intensity has been reached since January 2018. The fighting has continued, although not always with the same intensity and on the same scale, and hence there is a non-international conflict between the Yemeni Government and the South Transitional Council.

Organization

A series of indicative factors are used to assess whether armed groups exhibit to required degree of organization, such as the existence of a command structure and disciplinary rules and mechanisms, the ability to procure, transport, and distribute arms, the ability to plan, coordinate and carry out military operations, the ability to negotiate and conclude agreements, e.g. cease fire or peace agreements. If the criterion of a minimum organization of the armed groups is not fulfilled, there is no armed conflict. For further information, see 'non-international armed conflict - organization' in our classification section.

There are multiple armed groups and tribal militia active in Yemen. While for many of them not enough information is available to analyse their degree of organization, the Houthis, al-Qaeda in the Arabian Peninsula (AQAP), and the Southern Transitional Council undoubtedly have a sufficient degree of organization.

The Houthis

Originally founded to promote Zaidi Islam, the Houthis have been involved in a non-international armed conflict with the government since 2004. While little is known about the group itself apart from its leadership figures, they control significant parts of territory in Yemen, including the capital Sana’a since September 2014, which indicates that they are sufficiently organized to sustain military operations over a long period of time and to act as de facto authorities. This conclusion is reinforced by their ability to launch attacks on strategic targets such as oil facilities and airports in both Saudi Arabia and the UAE. Charles Schmitz, ‘The Huthi Ascent to Power’, Middle East Institute, 15 September 2014; S. Al Batati, ‘Who are the Houthis in Yemen’, Al Jazeera, 20 March 2015; Cameron Glenn, ‘Who are Yemen’s Houthis?’, Wilson Center, 29 April 2015; ‘Timeline: Houthi’s drone and missile attacks on Saudi targets’, Al Jazeera, 14 September 2019; Brian Carter, ‘January 2022 Map Update: Al Houthi Attacks on Saudi Arabia and the UAE’, Critical Threats, 19 January 2022; ‘Why did the Houthis attack the UAE? Everything you need to know’, Al Jazeera, 31 January 2022; ‘Yemen’s Huthi rebels call truce after wave of attacks on Saudi Arabia’, France 24, 26 March 2022; Jennifer Holleis and Kersten Knipp, ‘Houthi attacks expose Saudi Arabia’s defense weakness’, DW, 30 March 2022. Moreover, they succeed in arming themselves on a large scale with ballistic missiles and other modern weaponry, such as drones, despite international arms embargoes. Seth G. Jones, Jared Thompson, Danielle Ngo, Brian McSorley and Joseph S. Bermudez Jr., ‘The Iranian and Houthi War against Saudi Arabia’, Center for strategic and international Studies, 21 December 2021; ‘Iran ‘likely’ smuggling weapons to Yemen: UN report’, Al Jazeera, 9 January 2022; UN Panel of Experts on Yemen, ‘Final report of the Panel of Experts on Yemen established pursuant to Security Council resolution 2140 (2014)’, UN Doc S/2022/50, 26 January 2022, pp 23-33; Robert Tollast, ‘What ballistic missiles do the Houthis have and how do they get them?’, The National News, 24 January 2022. Furthermore, it becomes apparent that they were able to procure and provide military training as well as engaging in the negotiation of cease fire agreements and other political negotiations. They even have their own television station, which was used to announce their plans to take over Sana'a and to call on their supporters to take to the streets to protest against the government. Peter Salisbury, ‘Yemen: Stemming the Rise of a Chaos State’, Chatham House, 25 May 2016, p 21; Marc Daou, ‘Why Yemen’s Houthis turned down Saudi Arabia’s ceasefire offer’, France 24, 24 March 2021; ‘Yemen Houthis welcome talks with Saudi-led coalition, but in a neutral country’, Reuters, 16 March 2022; Jennifer Bell, ‘Houthi official rejects GCC offer to host Yemen peace talks in Saudi Arabia’, The Medialine, 17 March 2022; ‘Yemen’s Huthi rebels call truce after wave of attacks on Saudi Arabia’, France 24, 26 March 2022; ‘UN welcomes announcement of two-month truce in Yemen’, UN News, 1 April 2022.

Al Qaeda in the Arabian Peninsula

Al-Qaeda in the Arabian Peninsula (AQAP) was formed by the merger of the Yemeni and Saudi branches of al-Qaeda in 2009. In 2011, an offshoot of the group, Ansar al-Shari’a Yemen, seized control over large areas in the south, declaring them ‘Emirates’. However, the exact relationship between Ansar al-Shari’a Yemen and al-Qaeda in the Arabian Peninsula is not known, with many considering that the former is a simply naming exercise in order to attract more local fighters and to separate their foreign policy goals from their domestic goals. Stanford University, Mapping Militant Organisations: Al Qaeda in the Arabian Peninsula, 12 May 2015; S. Haddad, ‘Yemen’, in L. Arimatsu and M. Choudhury (eds), The Legal Classification of the Armed Conflicts in Syria, Yemen and Libya, Chatham House, 2014, pp. 26. Little information is available about the group. Nevertheless, their ability to control territory in the south, then declare them Emirates and then govern them, is a strong indication of AQAP's organisational capacity. Moreover, their ability to sustain concerted military operations against both government forces and Houthis suggests that the group exhibits the required degree of organization. They have also cooperated as an organisation with the anti-Houthi forces and actively participated in the popular resistance fronts formed in Abyan, Aden, Al Dali, Lahij, Shabwah and Taizz.  Peter Salisbury, ‘Yemen: Stemming the Rise of a Chaos State’, Chatham House, 25 May 2016, p 13; ‘Yemen’s al-Qaeda: Expanding the Base’, International Crisis Group, 2 February 2017, p I; Sari Arraf, ‘The Armed Conflict in Yemen: A Complicated Mosaic’, Geneva Academy, October 2017, p 9; Andrea Carboni and Matthias Sulz, ‘The wartime transformation of AQAP in Yemen’, ACLED Data, 14 December 2020. It should be noted that recently AQAP became weakened and more fragmented, which might indicate that the organizational threshold is not met any more. However, this conclusion seems to be premature at the moment. Elisabeth Kendall, ‘Where is AQAP now?’, Sana’a Center for Strategic Studies, 21 October 2021.

The Southern Transitional Council

The Southern Transitional Council (STC) was established in May 2017 by Aydrous al-Zubaidi. It was a reaction against the Hadi Government’s failure of governing over south Yemen. Immediately, a 26-seat council was installed and presided by former Aden governor Aydrous al-Zubaidi. With the emergence of the STC, the separatist movement gained ground and became an organised resistance movement not only against the Houthis, but also against the Government. The fact that their structure is so state-like and that there is a clear leadership, shows that they are an organized entity. ‘Yemen: What is het Southern Transitional Council?’, Al Jazeera, 26 April 2020; Peter Salisbury, ‘Yemen’s Southern Transitional Council: a delicate balancing act’, International Crisis Group, 30 March 2021.

Little information is available about the military structure of the STC. However, we know that the ‘Security Belt’ forces, a paramilitary formation trained by the UAE, was incorporated in the organization and became the STC’s military wing. They had one leader in charge of running this military wing, Munir al-Yafei, indicating the existence of a command structure. Moreover, they had the ability to control territory in the south, in particular in and around Aden. ‘What is the future of the Southern Transitional Council’, Abaad Studies & Research Center, 28 October 2021; Emile Roy and Muaz A., ‘The State of Yemen: Q3 2021 - Q4 2021', ACLED Data, 8 February 2022. Furthermore, given their continuing engagements with both government forces and Houthi forces, we can assume that they possess the ability to sustain concerted military operations. In addition, their involvement in the Riyadh accords illustrates their ability to speak with one voice and to negotiate ceasefire agreements and other types of political settlements. Ibrahim Jalal, ‘The Riyadh Agreement: Yemen’s new cabinet and what remains to be done’, Middle East Institute, 1 February 2021.

Saudi-led coalition

Purportedly put under House arrest following the Houthi takeover of the capital, President Hadi resigned in January 2015, but he rescinded his resignation after fleeing to Aden, the second largest city, in February 2015. He fled the country in March 2015 after the Houthis advanced towards Aden. ‘Yemen President Quits Amid Worsening Crisis’, Al Jazeera, 22 January 2015.  M. Ghobari and M. Mukhashaf, ‘Yemen’s Hadi Flees to Aden and Says he is still President’, Reuters, 21 February 2015; ‘Yemen President Flees Country as Country’s Turmoil Worsens’, Associated Press, 25 March 2015. Upon request of President Hadi, an international coalition led by Saudi Arabia launched airstrikes against Houthi rebels in Yemen. Saudi Arabia, Bahrain, Qatar, Kuwait and the United Arab Emirates cite extensively from the letter sent by President Hadi in their joint letter to the Security Council, see Idential Letters Dated 26 March 2015 from the Permanent Representative of Qatar to the United Nations Addressed to the Secretary-General and the President of the Security Council, UN doc S/2015/217, 27 March 2015. The intervention takes place with the consent of Yemen due to the request by President Hadi and hence does not affect the classification of the conflict. For further information, see the classification section. Admittedly, the validity of the consent is subject to debate because the legitimacy of President Hadi is contested. For a thorough discussion and comparing the situation of Yemen with the situation in Crimea, see T. Ruys and L. Ferro, ‘Weatherin the Storm: Legality and Legal Implications of the Saudi-Led Military Intervention in Yemen’, 65 International and Comparative Law Quarterly 1 (2016), p 81 ff.

Initially, airstrikes were launched by Saudi Arabia and the United Arab Emirates, with Kuwait, Bahrain, Qatar, Morocco, Sudan and Egypt to have contributed aircraft. ‘Yemen Air Strikes: A Guide to the Countries Backing Saudi Arabia’, Associated Press, 10 April 2015. In late 2015, Saudi Arabia, Bahrain, Qatar, the United Arab Emirates, Sudan, Morocco and Egypt also sent ground troops to Yemen. ‘Number of Saudi-led coalition troops in Yemen “rises to 10,000”’, Reuters, 8 September; S. Al-Batati and K. Fahim, ‘Foreign Ground Troops Join Yemen Fight’, The New York Times, 3 August 2015; ‘Qatar Sends 1,000 Ground Troops to Yemen Conflict’, Reuters, 7 September 2015; ‘Sudan Sends Ground Troops to Yemen to Boost Saudi-led Coalition’, Reuters, 18 October 2015; ‘Egypt Sends Up to 800 Ground Troops to Yemen’s War – Egyptian Security Sources’, Reuters, 9 September 2015; ‘Morocco Sends Ground Troops to Fight in Yemen’, Gulf News, 5 December 2015. The coalition led by Saudi Arabia is accused of systematic violations of international humanitarian law. See for example, Human Rights Watch, ‘UN: Suspend Saudi Arabia From Human Rights’, 29 June 2016. In its January 2016 report, the United Nations Panel of Experts on Yemen concluded that in some cases, the Saudi-led coalition violated the principle of distinction in a ‘widespread and systematic manner’. Final Report of the Panel of Experts on Yemen Pursuant to Security Council Resolution 2140 (2014), UN Doc S/2016/73; § 128. Against this background, the support of the United States and the United Kingdom to Saudi Arabia has received intense scrutiny, including the question whether their role suffices to render them a party to armed conflict against the Houthis under the ‘material support’ approach. On the material support approach, see the Classification section. The question remains debated, see for example B. Wille, ‘We Need to Know More About the US’s Role in Yemen’, Just Security Blog, 22 April 2016; R. Goodman, ‘If US and UK Have Joined the Fighting in Yemen, What’s Their Duty to Investigate Alleged Saudi War Crimes?’, Just Security Blog, 20 October 2016.

The coalition has been active in Yemen ever since their deployment to support President Hadi's government. Matthias Sulz and Sam Jones, ‘Over 100,000 reported killed in Yemen war’, ACLED, 19 October 2019; Global Conflict Tracker, ‘War in Yemen’, Council on Foreign Relations, 13 April 2022. As discussed under "intensity", fighting between the Houthis and the Saudi-led coalition escalated in late 2021, early 2022. This illustrates their continuing engagement in the NIAC with the Houthis.

United States

The United States has been undertaking drone airstrikes and ground operations against al-Qaeda in the Arabian Peninsula. Since 2009, the United States has conducted drone strikes against AQAP with the consent of the government of Yemen, which raises the question whether, in particular after 2011, they became a party to the non-international armed conflict between the Yemeni government and al-Qaeda in the Arabian Peninsula. The United States claimed that their drone strikes took place to pursue their own counter-terrorism efforts, targeting high level operatives, and that the United States 'was not working with the Yemeni government in terms of direct action or lethal action as part of that insurgency'. Transcript of John Brennan’s Remarks, 'U.S. Policy Toward Yemen', Council on Foreign Relations, 2012. Yet, against the background of the insurgency in Yemen, the United States' drone strikes and the scope of their mission more generally broadened to include wider support to the government against the insurgency by al-Qaeda in the Arabian Peninsula Hence, the United States is considered a party to the conflict. See D. Pearlstein, 'The Yemen War', Opinio Juris Blog,18 July 2012;  R. Chesney, 'Reactions to the ACLU Suit: There is Armed Conflict in Yemen, and the US Is Party to it', Lawfare Blog, 18 July 2012.

The U.S. continued their operations against AQAP in Yemen. In 2016, 35 airstrikes were carried out and in 2017 about 130 airstrikes were directed at AQAP and militants associated with the self-proclaimed Islamic State. Since then, the number of airstrikes carried out has decreased, but they are still taking place, which confirms continued U.S. involvement. Micah Zenko and Jennifer Wilson, ‘How Many Bombs Did the United States Drop in 2016?’, Council on Foreign Relations, 5 January 2017; Jessica Purkiss and Jack Serle, ‘Yemen: reported US covert actions 2017’, The Bureau of Investigative Journalism; ‘The War in Yemen’, New America; Luke Hartig and Oona Hathaway, ‘Still at War: The United States in Yemen’, Just Security, 24 March 2022; Kali Robinson, ‘Yemen’s Tragedy: War, Stalemate, and Suffering’, Council on Foreign Relations, 8 April 2022.

Yemen is a party to the four 1949 Geneva Conventions. All parties to the conflict are bound by Article 3 common to the 1949 Geneva Conventions that provides for the minimum standard to be respected and requires humane treatment without adverse distinction of all persons not or no longer taking active parts in hostilities. It prohibits murder, mutilation, torture, cruel, inhuman and degrading treatment, hostage taking and unfair trials.

Yemen is also a party to the 1977 Additional Protocol II applicable to non-international armed conflicts. The ability of the Houthis and al-Qaeda of the Arabian Peninsula to exercise territorial control over large parts of Yemen suggests that they fulfil the required criterion for the applicability of Protocol II, namely the ability to carry out sustained and concerted military operations; impose discipline; and the ability to implement Protocol II. In this sense, see also S. Haddad, ‘Yemen’ in L. Arimatsu and M. Choudhury (eds), The Legal Classification of the Armed Conflicts in Syria, Yemen and Libya, Chatham House, 2014, p 30. However, Protocol II does not apply between armed groups. All parties are bound by customary international humanitarian law applicable to non-international armed conflicts. Customary international law consists of unwritten rules that come from a general practice accepted as law. Based on an extensive study, the International Committee of the Red Cross maintains a database on customary international humanitarian law.

In addition to international humanitarian law, international human rights law continues to apply during times of armed conflict. Under human rights law, the territorial state has an obligation to prevent and to investigate alleged violations, including by non-state actors. Non-state armed groups are increasingly considered to be bound by international human rights law if they exercise de facto control over some areas.

State parties

• Bahrain

• Jordan

• Egypt

• Kuwait

• Saudi Arabia

• Sudan

• United Arab Emirates

• United States

• Yemen

 

Non-state parties

A myriad of armed groups are active in Yemen. Below is a selection of the key armed groups. For a more detailed overview of other armed groups, see  S. Haddad, ‘Yemen’ in L. Arimatsu and M. Choudhury (eds), The Legal Classification of the Armed Conflicts in Syria, Yemen and Libya, Chatham House, 2014, p 25-26; Mapping the Yemen Conflict, European Council on Foreign Relations, 2016. Alliances between the armed groups are fluid and frequently shifting.

• Houthi
• Al-Qaeda in the Arabian Peninsula
• Southern Transitional Council (STC)