The War Against ISIS: How Kurdish Forces Fought and Defeated the Islamic State
- Mehmet Özdemir
- May 24
- 13 min read
Introduction
The war against the Islamic State of Iraq and Syria (ISIS) was one of the defining conflicts of the early twenty-first century. For the Kurdish people, it was both an existential crisis and a moment of extraordinary military achievement. Between 2014 and 2019, Kurdish forces on two major fronts — the Peshmerga in Iraq and the YPG/YPJ-led Syrian Democratic Forces (SDF) in Syria — fought and ultimately defeated the most powerful jihadist army the modern Middle East had ever seen.
The war began with catastrophe. In June 2014, ISIS swept across northern Iraq, seizing Mosul, Tikrit, and vast stretches of territory while the Iraqi army collapsed. Within weeks, ISIS launched an offensive into Kurdish-held areas, threatening Erbil and committing genocide against the Yazidi population of Sinjar. In Syria, ISIS besieged the Kurdish city of Kobani in a battle that became a global turning point. What followed was a grinding multi-year campaign that saw Kurdish fighters — often outgunned, under-resourced, and caught between hostile states — liberate city after city, from Sinjar to Manbij to Raqqa to Baghuz.
This article covers the full arc of the Kurdish war against ISIS across both Iraq and Syria, from the initial shock of 2014 through the territorial defeat of the caliphate in March 2019 and the painful aftermath that followed, including the Kurdistan independence referendum crisis of 2017.
Contents
The Rise of ISIS
The Islamic State of Iraq and Syria emerged from the wreckage of the post-2003 Iraqi insurgency. Originally known as Al-Qaeda in Iraq under Abu Musab al-Zarqawi, the group evolved through several iterations before Abu Bakr al-Baghdadi declared a caliphate in June 2014 from the Great Mosque of al-Nuri in Mosul. At its peak, ISIS controlled territory roughly half the size of the United Kingdom, spanning from eastern Syria to western Iraq, governing millions of people under a brutal interpretation of Islamic law.
The group's military capability was formidable. It had captured enormous quantities of American-supplied military equipment abandoned by the collapsing Iraqi army, including armoured vehicles, artillery, and anti-aircraft weapons. Its ranks included experienced former Baathist military officers alongside thousands of foreign fighters drawn from across the world. Its use of social media for propaganda and recruitment was unprecedented, and its willingness to commit mass atrocities — beheadings, crucifixions, sexual slavery, and ethnic cleansing — spread terror far beyond the battlefield.
The Fall of Mosul and the Kurdish Frontline
On 10 June 2014, ISIS fighters stormed Mosul, Iraq's second-largest city. An estimated 800 to 1,500 militants routed an Iraqi garrison of approximately 30,000, triggering one of the most dramatic military collapses in modern history. The fall of Mosul was followed by the capture of Tikrit, Baiji, and much of Anbar and Nineveh provinces. The Iraqi army's northern divisions effectively ceased to exist.
With the Iraqi state in retreat, the Kurdistan Region's Peshmerga forces became the primary ground force confronting ISIS across a frontline that stretched over 1,000 kilometres. The Peshmerga moved into disputed territories including Kirkuk, which they had long claimed, filling the vacuum left by the retreating Iraqi army. However, the Peshmerga themselves were stretched thin, poorly equipped for conventional warfare against an enemy wielding tanks and artillery, and divided between KDP and PUK command structures.
On 7 August 2014, ISIS forces advanced to within 40 kilometres of Erbil, the capital of the Kurdistan Region. US President Barack Obama authorised airstrikes the same day, marking the beginning of the American-led military intervention that would prove decisive in supporting Kurdish ground forces on both the Iraqi and Syrian fronts.
The Sinjar Massacre and the Yazidi Genocide
On 3 August 2014, ISIS launched an assault on the Sinjar district of Nineveh province, home to the largest concentration of Yazidi Kurds in Iraq. The Peshmerga forces stationed in the area withdrew without engaging in sustained fighting, a decision that remains deeply controversial. Thousands of Yazidi families were left exposed.
What followed was genocide. ISIS fighters systematically separated men from women and children. Men and older boys were executed in mass shootings. Women and girls were taken as sexual slaves, distributed among fighters, and trafficked across ISIS-held territory. The United Nations estimates that approximately 5,000 Yazidis were killed, while between 4,200 and 10,800 were kidnapped or held captive. Approximately 500,000 Yazidis were displaced. Thousands fled to Mount Sinjar, where they were besieged without food, water, or shelter in the August heat.
The crisis on Mount Sinjar prompted international intervention. The United States, United Kingdom, and other coalition partners carried out emergency airdrops of humanitarian supplies. Critically, fighters from the PKK and the Syrian YPG crossed from Rojava and opened a humanitarian corridor through the mountains, allowing tens of thousands of Yazidis to escape to safety in Syria and then into the Kurdistan Region. This rescue operation marked the first significant YPG-PKK cooperation on Iraqi soil and established a foothold that would later lead to the creation of the Sinjar Resistance Units (YBS).
The Yazidi genocide was formally recognised by the United Nations, the European Parliament, and numerous national governments. It is often referred to as the 74th genocide in Yazidi collective memory — a reference to the community's long history of persecution.
The Siege of Kobani
The siege of Kobani (Ayn al-Arab) was the single most important battle in the war against ISIS and the moment that transformed Kurdish forces from a regional concern into a global ally. Beginning in mid-September 2014, ISIS massed an estimated 4,000 fighters supported by tanks, artillery, and rocket launchers on three sides of the small Syrian-Kurdish border city. Over 130,000 civilians fled across the Turkish border as ISIS overran dozens of surrounding villages.
The YPG and YPJ defenders, numbering only a few hundred initially, fought street by street in conditions of extreme disadvantage. The battle was broadcast live on international television from the Turkish side of the border, and the spectacle of Kurdish fighters — including prominent women fighters of the YPJ — holding out against overwhelming odds captured global attention.
US-led coalition airstrikes began targeting ISIS positions around Kobani on 27 September 2014. On 19 October, the US carried out airdrops of weapons and ammunition to the YPG — a politically fraught decision given Turkish opposition to arming a group linked to the PKK. In late October, Iraqi Peshmerga reinforcements crossed through Turkey with heavy weapons, providing critical artillery support. Free Syrian Army fighters also joined the defence.
By late January 2015, the YPG had recaptured the city. The battle reportedly killed over 1,000 ISIS fighters and 324 YPG/YPJ combatants. Kobani was ISIS's first major territorial defeat and shattered the narrative of the group's invincibility. It also established the YPG as the primary ground partner of the US-led coalition in Syria — a relationship that would define the rest of the war.
The Formation of the Syrian Democratic Forces
In October 2015, the Syrian Democratic Forces (SDF) were formally established as a multi-ethnic military alliance. While the YPG remained its dominant component, the SDF included Arab, Syriac-Assyrian, Turkmen, and Armenian militias. The formation was partly a diplomatic device — creating a broader umbrella allowed the United States to support Kurdish-led operations without appearing to arm a purely Kurdish or PKK-linked force, which would have further antagonised Turkey.
The SDF's structure reflected the political model of the Autonomous Administration of North and East Syria (Rojava), which emphasised multi-ethnic governance, gender parity, and democratic confederalism. Its military wing included the YPJ (Women's Protection Units), one of the few all-female combat forces in any active conflict, which played a significant role in virtually every major engagement against ISIS.
Key Battles in Iraq: Mosul Dam, Kirkuk, and Makhmour
The Battle of Mosul Dam (August 2014)
On 3 August 2014, ISIS captured the Mosul Dam, Iraq's largest, threatening a catastrophic flood that could have devastated Mosul and Baghdad. On 17-18 August, Peshmerga forces supported by US airstrikes recaptured the dam in one of the first successful joint operations of the war. The battle demonstrated that Kurdish forces, when backed by coalition air power, could defeat ISIS in conventional engagements.
The Defence of Kirkuk (2014)
ISIS launched repeated offensives against Kirkuk city and its surrounding areas from July to November 2014. Peshmerga forces, supplemented by PKK fighters and local volunteers, defended the city in sustained fighting. The battle for Kirkuk had deep symbolic significance for Kurds, who had long claimed the oil-rich city as historically Kurdish.
The Makhmour and Gwer Fronts
The Makhmour and Gwer fronts, south and southwest of Erbil, saw some of the war's most intense fighting in 2014. ISIS used vehicle-borne improvised explosive devices, tunnels, and waves of fighters to attempt breakthroughs toward the Kurdish capital. Peshmerga forces, often fighting with ageing Soviet-era weapons against American-made armour captured from the Iraqi army, held these positions at significant cost.
The Liberation of Sinjar
In November 2015, a combined force of Peshmerga, YPG/PKK-affiliated units, and Yazidi fighters launched Operation Free Sinjar. Supported by US-led coalition airstrikes, the offensive cut the strategic Highway 47 connecting Mosul to Raqqa — ISIS's main supply route between its Iraqi and Syrian territories. The town of Sinjar was recaptured, although much of it had been destroyed.
The liberation of Sinjar was militarily significant but politically complex. Tensions between the KDP-aligned Peshmerga and PKK-affiliated Sinjar Resistance Units (YBS) over control of the area persisted long after ISIS was driven out, creating a proxy conflict that continues to shape Yazidi politics.
The Battles of Manbij, Tabqa, and the Road to Raqqa
After Kobani, the SDF launched a series of offensives that systematically dismantled ISIS's territorial control in northern Syria. In June 2015, SDF forces captured Tell Abyad, linking the Kobani and Jazira cantons for the first time. In December 2015, the Tishrin Dam offensive secured another key crossing over the Euphrates.
The Manbij offensive (June-August 2016) was a major operation that liberated the predominantly Arab city from ISIS control. The battle was significant both militarily and politically — it demonstrated the SDF's ability to operate beyond traditionally Kurdish areas and showed the multi-ethnic coalition in action, though Turkey strongly opposed the YPG's westward advance across the Euphrates.
In March-May 2017, the SDF captured the Tabqa Dam and the nearby town of Tabqa in a daring operation that included a US-supported airborne river crossing. This cleared the final major obstacle before Raqqa itself.
The Battle of Raqqa
The battle of Raqqa was the culmination of the Syrian campaign against ISIS. Beginning on 6 June 2017, SDF forces — predominantly YPG and YPJ fighters supported by Arab components — attacked from the north, east, and west while the Euphrates River blocked the southern approach. The operation was backed by intensive US-led coalition airstrikes, special forces advisors, and artillery support.
The fighting was brutal. ISIS had heavily fortified the city with tunnels, IEDs, snipers, and vehicle bombs. Entire neighbourhoods were reduced to rubble by airstrikes and ground combat. Thousands of civilians were trapped inside the city throughout the four-month battle. Human rights organisations documented significant civilian casualties from both ISIS tactics and coalition bombing.
On 17 October 2017, the SDF declared the full capture of Raqqa. ISIS's self-proclaimed capital had fallen. The city's National Hospital and al-Naim Roundabout — where ISIS had conducted public executions — became symbols of the group's defeat. The SDF had lost hundreds of fighters in the battle. The fall of Raqqa, combined with the Iraqi liberation of Mosul three months earlier in July, effectively ended ISIS as a territorial state.
The Battle of Baghuz and the End of the Caliphate
After the fall of Raqqa, the SDF continued operations along the Euphrates valley in Deir ez-Zor province throughout 2018 and into early 2019. The final territorial battle took place at Baghuz, a small riverside village near the Iraqi border where the remnants of ISIS made their last stand.
Thousands of ISIS fighters and their families surrendered during the months-long siege, including hundreds of foreign fighters and over 4,000 family members. They were transferred to SDF-administered detention camps, most notably the al-Hol camp, which grew to hold over 70,000 people and became a significant security and humanitarian crisis in its own right.
On 23 March 2019, the SDF declared the total territorial defeat of ISIS at Baghuz. The caliphate that had once stretched across large parts of Iraq and Syria, ruling millions, was finished as a geographic entity. ISIS leader Abu Bakr al-Baghdadi was killed in a US special forces raid in northwest Syria in October 2019.
The 2017 Kurdistan Referendum Crisis
On 25 September 2017, the Kurdistan Regional Government held an independence referendum. Over 92 percent of voters chose independence. The referendum was held not only in the Kurdistan Region's recognised territory but also in disputed areas including Kirkuk, which the Peshmerga had controlled since 2014.
The reaction was swift and punitive. The Iraqi government, backed by Iran-supported Popular Mobilisation Forces (PMF), launched a military operation on 16 October 2017. Iraqi forces retook Kirkuk — a city of enormous symbolic and economic importance to the Kurdish cause — with minimal resistance after elements of the PUK-aligned Peshmerga withdrew. The KRG also lost control of disputed territories in Sinjar, Makhmour, Khanaqin, and Tuz Khurmatu.
The loss of Kirkuk was the most painful territorial reversal for the Kurdistan Region since 2003. Coming just weeks after Kurdish forces had been instrumental in liberating Mosul and Raqqa from ISIS, the referendum crisis exposed the limits of Kurdish military and political power within a hostile regional environment. The United States, despite its deep partnership with the Peshmerga, did not intervene to prevent the Iraqi advance.
Legacy and Aftermath
The Kurdish war against ISIS produced several lasting consequences. The Peshmerga were confirmed as a battle-tested conventional military force, though their structural weaknesses — divided command, ageing equipment, and dependence on external support — were equally exposed. The YPG/YPJ and SDF gained international recognition and US military partnership, but also drew the permanent hostility of Turkey, which conducted military operations against Kurdish-held Afrin (2018), Ras al-Ayn and Tell Abyad (2019), and continued strikes through 2024-2025.
An estimated 1,800 Peshmerga fighters were killed in the war against ISIS. SDF casualties across all operations numbered in the thousands. The human cost among civilians, particularly the Yazidi community, was catastrophic and continues to shape Kurdish politics and identity.
The war also deepened intra-Kurdish divisions. The KDP-PUK rivalry, the PKK's expanded presence in Sinjar and the Kurdistan Region, and the political relationship between the SDF and the KRG remain sources of tension. ISIS itself was never fully destroyed — its insurgent networks continue to operate in both Iraq and Syria, carrying out attacks on Kurdish and Arab forces alike.
For the Kurdish people, the war against ISIS was a moment of extraordinary courage and sacrifice. Kurdish fighters — men and women — stood and fought when many of the region's larger armies would not. Their contribution to the defeat of the most dangerous terrorist organisation of the modern era is a matter of historical record, whatever political disputes continue to surround the aftermath.
Key Events and Timeline
June 2014 — ISIS captures Mosul; Iraqi army collapses across northern Iraq
August 2014 — Sinjar massacre and Yazidi genocide begins; ISIS advances toward Erbil; US airstrikes begin; Peshmerga and US forces recapture Mosul Dam
September 2014 — ISIS besieges Kobani; US-led coalition airstrikes begin in Syria
January 2015 — YPG declares Kobani liberated from ISIS
October 2015 — Syrian Democratic Forces (SDF) formally established
November 2015 — Joint Kurdish offensive liberates Sinjar
June-August 2016 — SDF captures Manbij from ISIS
June-October 2017 — Battle of Raqqa; SDF captures ISIS capital on 17 October
September 2017 — Kurdistan independence referendum; 92% vote yes
October 2017 — Iraqi forces retake Kirkuk and disputed territories from Peshmerga
March 2019 — SDF captures Baghuz; ISIS territorial caliphate declared defeated
October 2019 — ISIS leader Abu Bakr al-Baghdadi killed in US raid
Frequently Asked Questions
What role did Kurdish forces play in the war against ISIS?
Kurdish forces played the leading ground combat role on two major fronts. In Iraq, the Peshmerga defended the Kurdistan Region, recaptured Mosul Dam, and helped liberate Sinjar and Mosul. In Syria, the YPG/YPJ-led SDF became the primary ground partner of the US-led coalition, capturing Kobani, Manbij, Raqqa, and Baghuz.
What was the Battle of Kobani?
The siege of Kobani (September 2014 to January 2015) was a pivotal battle in which YPG and YPJ fighters defended the Syrian-Kurdish border city against an ISIS force of approximately 4,000 fighters. Supported by US-led coalition airstrikes and Iraqi Peshmerga reinforcements, the defenders recaptured the city, inflicting ISIS's first major territorial defeat.
What happened during the Sinjar massacre?
On 3 August 2014, ISIS attacked the Sinjar district, home to Iraqi Yazidi Kurds. After Peshmerga forces withdrew, ISIS carried out a genocide — killing an estimated 5,000 Yazidis, kidnapping thousands more, and enslaving women and girls. Hundreds of thousands were displaced. PKK and YPG fighters later opened a corridor to rescue those trapped on Mount Sinjar.
What was the SDF?
The Syrian Democratic Forces (SDF) were established in October 2015 as a multi-ethnic military alliance led by the Kurdish YPG. The SDF included Arab, Syriac-Assyrian, Turkmen, and Armenian components. It served as the primary ground force of the US-led coalition in Syria and was responsible for the capture of Raqqa and the defeat of ISIS's territorial caliphate.
When was ISIS defeated?
ISIS was defeated as a territorial entity on 23 March 2019, when the SDF captured Baghuz, the last pocket of land held by the group. However, ISIS was never fully destroyed as an insurgent organisation and continues to carry out attacks in Iraq and Syria.
What happened after the 2017 Kurdistan independence referendum?
Following the referendum on 25 September 2017, in which over 92 percent voted for independence, the Iraqi government launched a military operation to retake disputed territories. Iraqi and PMF forces recaptured Kirkuk on 16 October 2017 with minimal resistance, and the KRG lost control of Sinjar, Makhmour, Khanaqin, and other disputed areas.
How many Kurdish fighters were killed in the war against ISIS?
An estimated 1,800 Peshmerga fighters were killed in Iraq. SDF casualties across all operations in Syria numbered in the thousands, though precise figures are difficult to verify. Thousands more were wounded across both fronts.
Did Kurdish women fight against ISIS?
Yes. The Women's Protection Units (YPJ) were one of the most prominent all-female combat forces in any modern conflict. YPJ fighters participated in virtually every major battle against ISIS in Syria, including Kobani, Manbij, Raqqa, and Baghuz. Female Peshmerga fighters also served on the Iraqi front.
References and Further Reading
Wilson Center — Timeline: The Rise, Spread, and Fall of the Islamic State
Human Rights Watch — Reports on Sinjar, Anfal, and ISIS atrocities in Iraq and Syria
United Nations Human Rights Council — Report on ISIS crimes against the Yazidi community
BBC News — Coverage of the Siege of Kobani, Battle of Raqqa, and Kurdish frontlines
Reuters / Associated Press — Reporting on Peshmerga operations, SDF campaigns, and the Kurdistan referendum
Air and Space Forces Magazine — The Siege of Kobani: Coalition airpower in the battle
Washington Institute — Iraqi Yazidis: Trapped Between the KDP and the PKK
PBS Frontline — Confronting ISIS: The role of US-Kurdish partnership
International Crisis Group — Reports on the Kurdistan independence referendum and its aftermath
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