People's Defense Units

Overview

The People’s Defense Units, commonly known by the initials YPG, are a Kurdish-led armed organization formed during the Syrian civil war. Linked to the Democratic Union Party, or PYD, the YPG became the military backbone of the Syrian Democratic Forces, or SDF. It helped establish Kurdish-led control across parts of northern and northeastern Syria, fought the Islamic State, and worked with the United States in the campaign against that organization. Its relationship with the Kurdistan Workers’ Party, or PKK, has shaped both its leadership and Turkey’s military policy toward it.

The YPG’s record combines a consequential role in defeating the Islamic State with a territorial and political struggle that outlasted that campaign. Its defense of Kobani became a turning point in cooperation with United States forces. Its expansion elsewhere in northern Syria brought it into conflict with the Islamic State, Ankara-backed rebels and forces loyal to Bashar al-Assad. Turkey, which designates the YPG a terrorist organization because of its PKK affiliation, launched offensives to remove it from the border. After Assad’s fall, the YPG’s position became bound to negotiations over whether SDF fighters would remain under local command or enter a new Syrian army as individuals.

Founding and ideology

The YPG emerged as the armed force associated with the PYD as state authority weakened in northern Syria. Kurdish forces took control of Kobani at the end of July 2012, and the YPG established itself in other northern areas during the first phase of the civil war. Its rise formed part of a broader effort to connect areas of Syrian Kurdistan under Kurdish-led administration. The PYD and its YPG militia later led the Autonomous Administration of North and East Syria, including during the period when control of Qamishli remained divided.

The organization’s political outlook was closely associated with the PYD and influenced by the PKK’s movement. The PKK supported the YPG during the war, while PKK veterans from Iraq took part in the fighting in Syria. An estimate of the YPG force fighting the Islamic State placed the share of PKK fighters who had arrived from Iraq at approximately half. The PKK also maintained links through positions in Sinjar and the Qandil Mountains, connecting its Iraqi bases to PKK-linked forces in Syria. These ties were significant to command, recruitment and Turkey’s assessment of the organization.

Kurds are a diverse people living across Turkey, Iraq, Iran and Syria. The YPG and the PKK represent particular armed movements within that wider population; neither represents every Kurdish community or political position. The YPG’s links to the PKK nevertheless remained a defining feature of its organization. Commanders who joined after the YPG’s establishment in 2012 had limited prospects for advancement without credentials earned through long-term PKK service. Promotion routes included ideological academies under direct PKK control in Qandil. PKK leaders based there consequently exercised deep influence over the YPG’s collective leadership.

History

During the civil war, Syria fragmented among competing forces. Assad’s troops and Iranian-backed militias held much of the west, Sunni armed factions operated across central areas, and Kurdish-led YPG forces controlled territory in the northeast. In 2012, the YPG gained control of Kobani as Assad’s forces withdrew from much of the area. Its subsequent expansion joined two of three Kurdish-led cantons in northeastern Syria, while its leaders sought a more continuous area of control. That ambition placed the organization at the center of contests over border crossings, towns and routes connecting northern Syria to the rest of the country.

The Azaz–Jarabulus belt in northwestern Syria was especially important because it provided a gateway to Aleppo. The YPG was one of several forces contesting it. Its rivals there included the Islamic State, Ankara-backed rebels and Assad-regime forces backed by Russia. Turkey opposed YPG expansion into Arab areas along its border and attacked the Jarablus area to prevent the organization from taking control. The fighting showed how the YPG’s campaign against the Islamic State intersected with a separate struggle over the future territorial shape of northern Syria.

After the SDF’s campaign against the Islamic State, the coalition controlled roughly 30 percent of Syria. Most of that territory lay east of the Euphrates River, although the SDF also held a handful of positions to its west. The YPG remained its core Kurdish force. The Women’s Protection Units, or YPJ, also held a prominent place in the coalition; together, the predominantly Kurdish YPG and YPJ were its most influential forces in 2025. SDF-held territory included areas whose population and political interests extended beyond the YPG’s original Kurdish base.

Turkey launched Operation Olive Branch against Afrin in January 2018. Ankara described the offensive as part of its wider campaign against the PKK and the YPG and sought to remove the YPG from its southern border. Turkish forces captured Afrin from the organization that year. The offensive caused large-scale Kurdish displacement: approximately 200,000 people, more than half of Afrin’s Kurdish population, left the area. The loss deprived the YPG of a major western position and deepened the geographic separation between Kurdish-led areas.

Later Turkish incursions drove approximately 70,000 Kurds from the area between Tal Abyad and Ras al-Ain. President Recep Tayyip Erdoğan sought a border buffer area that would suppress the YPG and accommodate Syrian refugees, including Sunni Arabs, in areas from which Kurds had fled. Ankara’s stated objectives for its northeastern campaign included establishing a zone extending to the Iraqi border, resettling millions of refugees and removing the YPG from Turkey’s border. At the time of a Washington Institute assessment, Turkey had not achieved those objectives. A strong United States reaction to its incursion also made Ankara reluctant to resume operations against the YPG for fear of sanctions.

Turkey’s offensive drew Assad’s forces and Russia further into the border confrontation. Russia deployed military police as a buffer and negotiated with both the YPG and Assad’s regime. Assad’s troops subsequently entered Kurdish-controlled areas including Manbij. The arrangement placed Russian forces between Turkish and Syrian troops while the YPG sought to preserve positions exposed by the Turkish advance. It also demonstrated that the YPG could cooperate tactically with Assad’s forces against an immediate Turkish threat despite their broader competition over authority in Syria.

Structure and leadership

The YPG functioned as an armed component of the PYD-led political and administrative system in northern Syria. Its commanders directed forces in Kurdish-majority areas and, through the SDF, took part in operations across a much larger territory. The SDF joined YPG and YPJ fighters with other local formations, including non-Kurdish forces. The YPG’s experienced units remained central to the coalition’s ability to conduct operations against the Islamic State, while the broader SDF structure allowed those operations to extend into areas outside the YPG’s original base.

The PKK’s influence reached beyond the presence of individual veterans. Commanders with long service under PKK control in Qandil held advantages in the YPG’s senior leadership structure. Fighters and junior commanders who entered the organization after 2012 faced barriers to promotion without those credentials. This hierarchy gave the Qandil-based PKK command deep influence over the organization while the YPG operated within a distinct Syrian battlefield and administration. The relationship was central to Turkey’s opposition to the YPG, including its objections to United States arms and training for SDF forces.

Mazloum Abdi commanded the SDF during its later negotiations with Damascus. His role concerned the future of the YPG’s forces as well as the wider coalition. The central question was whether existing formations would enter Syria’s army with their local command intact. The SDF sought to retain control of its troops and opposed Syrian army entry into its territory. Damascus pressed for authority over the fighters and the areas they held, making command structure a decisive issue rather than a matter of terminology alone.

Funding and sponsors

The PKK supplied personnel and organizational support to the YPG during the Syrian civil war. Fighters arriving from Iraq strengthened the organization during its campaign against the Islamic State, while the PKK’s Qandil leadership influenced training and advancement. Those contributions formed part of the YPG’s military development and help explain why Turkey treated the Syrian organization’s links to the PKK as a central security concern.

The United States became the YPG’s principal military partner in the campaign against the Islamic State. United States and coalition aircraft supported its defense of Kobani, and U.S. Special Forces later advised and assisted the YPG in Syria. The SDF partnership developed from that battlefield cooperation. Turkey opposed United States arms for the YPG because of its PKK relationship, leaving Washington’s counter-Islamic State partnership in persistent tension with Ankara’s border policy.

Attacks and operations

Fighting between Kurdish forces and the Islamic State spread to the Kobani area in summer 2014. The Islamic State mounted a major assault that drove the defenders from much of the surrounding countryside and pressed into the city. YPG forces fought prolonged street battles against its fighters. United States-led coalition aircraft struck Islamic State positions in support of the defense, beginning a strategic military partnership with Syrian Kurdish forces. Kurdish fighters held Kobani through months of close combat; coalition airstrikes inflicted heavy damage, but the ground force remained essential to the outcome.

Reports from the battle described possible Islamic State chemical-weapons use against Kurdish forces on October 21 and 22, 2014. The reported symptoms and photographs prompted concern, although contemporary accounts did not establish the agent used with certainty. Fighting remained intense late that year. Clashes on November 29 killed ten Islamic State fighters, and neither side had won a decisive victory by early December. Kurdish forces expelled the Islamic State from Kobani in January 2015 after more than four months of fighting. Combat continued in the surrounding countryside after the city’s recapture.

Kobani’s defense raised the YPG’s standing and strengthened prospects for cooperation among Syrian Kurdish forces, PKK-linked fighters from Turkey and Peshmerga forces from Iraq. It also established the YPG as a force capable of holding ground against a major Islamic State attack when supported by coalition airpower. That experience helped make its fighters the military backbone of the SDF. The coalition subsequently partnered with the United States across the broader campaign against the Islamic State, including operations associated with Operation Inherent Resolve.

The YPG’s operations also involved struggles with Turkey and other armed groups over northern Syria. In the Azaz–Jarabulus belt, its attempt to extend control brought it into a crowded battlefield involving Ankara-backed rebels, Assad-regime forces and the Islamic State. Turkey’s attack around Jarablus sought to block a YPG advance. The 2018 battle for Afrin then ended in a Turkish victory and major Kurdish displacement. Later fighting along the northeastern border renewed the contest over whether the YPG could retain positions adjacent to Turkey.

Designations and international status

Turkey designates the YPG and the YPG-led SDF as terrorist organizations because of their affiliation with the PKK. The PKK itself is designated a terrorist organization by both Turkey and the United States. Ankara’s designation of the YPG shaped its military offensives, its opposition to United States assistance and its demands concerning any future Syrian military role for YPG commanders. Turkey sought the removal of the YPG from its border even while YPG forces fought alongside the United States against the Islamic State.

The United States nevertheless treated the SDF as a counterterrorism partner. Its aircraft supported YPG fighters at Kobani, its Special Forces advised and assisted them, and its later cooperation with the SDF rested heavily on the YPG’s combat experience. The partnership against the Islamic State and the YPG’s PKK links were simultaneous features of the organization’s international position. Turkey’s concerns did not end with the battlefield campaign: it also rejected proposals that would allow SDF commanders to enter Syria’s military as officers while preserving their existing influence.

Current status

Assad’s fall in December 2024 opened negotiations between Syria’s new leadership and the SDF coalition built around the YPG. The new authorities sought to bring armed organizations under a unified Ministry of Defense while the SDF continued to face conflict with pro-Turkish forces in northeastern Syria. Ahmed al-Sharaa proposed including Kurdish forces in the ministry. During negotiations, he also said Syria would not permit PKK attacks to be launched from its territory, addressing a central Turkish demand.

On March 10, 2025, Abdi and al-Sharaa signed an accord calling for SDF forces to enter Syria’s army. The accord did not define how integration would occur. The SDF sought to retain local command and resisted Syrian army entry into its territory, citing security risks and inadequate guarantees after sectarian violence committed by Damascus’s forces elsewhere. Turkey demanded that SDF fighters join Syria’s military individually and opposed the entry of existing SDF commanders as officers. These conflicting positions left control of troops and territory unresolved despite the agreement.

A later integration framework favored Damascus on those central points. It required SDF fighters, including those from the YPG core, to enter Syria’s military as individuals rather than as intact units. It also expanded central government control over formerly SDF-held areas in Deir ez-Zor and Raqqa. Individual enlistment would transfer authority over fighters formerly organized around the YPG to the Syrian state and remove the local unit control the SDF had sought to preserve. The YPG’s future therefore became tied to the implementation of the wider SDF–Damascus settlement and to the continuing demands of Turkey along Syria’s northern border.