Battle of Mosul (2016–2017)

Overview

The Battle of Mosul was the campaign in which forces of Iraq and their allies retook Mosul from the Islamic State. Prime Minister Haider al-Abadi announced the operation on October 17, 2016. Iraqi security forces entered a prolonged urban battle, supported by Kurdish Peshmerga, Sunni tribal fighters, the Popular Mobilization Forces and aircraft of the American-led coalition. Iraqi forces defeated the Islamic State in eastern Mosul by January 2017, advanced into the western districts and completed the city’s recapture in July. The battle ended the group’s control of its last major stronghold in Iraq, though it continued to mount attacks after losing the city.

Mosul’s importance extended beyond its size. The Islamic State had seized it in 2014, and possession of a major city helped sustain its territorial rule and its claim to operate a state. At the start of the counteroffensive, Mosul was Iraq’s only major Sunni-majority city still under Islamic State control. Its recapture therefore carried military and political weight. Victory also exposed the costs of fighting through densely populated neighborhoods: an estimate placed civilian deaths during the battle between 9,000 and 11,000, roughly one million people left the city, and extensive damage made return difficult even after the fighting ended.

Background

The Islamic State’s 2014 capture of Mosul gave it control of a major Iraqi population center and an operational base in Nineveh province. Retaking the city became a central objective of Iraq’s campaign against the group. Iraqi forces liberated Fallujah in June 2016 and prepared for an attack on Mosul from Qayyarah, south of the city. Coalition strikes around Qayyarah and Sinjar supported that preparation. In September, the United States announced the deployment of another 600 troops to Iraq to assist the Mosul operation. American support included air power, training and personnel who directed strikes from Iraqi front lines after the battle began.

The force assembled around Mosul brought together partners with different interests. Iraqi security forces and Peshmerga led the ground campaign, while Shiite militias grouped in the Popular Mobilization Forces and Sunni tribesmen also participated. More than 30,000 coalition troops faced an Islamic State force estimated at fewer than 7,000 fighters in the city. Numbers and equipment favored the attackers, but the defenders held built-up terrain, prepared positions and access to civilians among whom they could hide. Their defense forced the coalition into months of street-by-street fighting.

The Nineveh Plains, east of Mosul, served as an approach to the city and formed part of the historic homeland of Assyrian Christians. Peshmerga fighters helped secure initial gains there before Iraqi federal forces attacked Mosul’s suburbs. Nineveh’s varied communities also shaped the political questions awaiting the victors. As liberation approached, Iraqis debated whether Nineveh province should become a region with newly drawn provinces. Proposals had implications for urban Mosul, rural Arab districts, the Nineveh Plains, Yazidi communities around Sinjar and Turkmen communities around Tall Afar. The coalition could agree on defeating the Islamic State without sharing one view of the province’s future government.

The campaign also unfolded amid concern about the influence of the regime in Iran. The Popular Mobilization Forces included powerful Shia militias controlled by the Iranian regime, whose Islamic Revolutionary Guard Corps oversaw its policy in Iraq. Their participation added substantial manpower to the anti-Islamic State effort while raising questions about Iraqi sovereignty and the balance of power after liberation. The competing interests within the coalition made its wartime alliance tenuous and ensured that victory in Mosul alone could not settle Iraq’s wider security and political disputes.

Course of the war

Al-Abadi announced the campaign on October 17, 2016, and Iraqi forces began by surrounding Mosul. The offensive advanced from the Nineveh Plains through outlying positions toward the city. American-led aircraft supported ground troops, and the United States sent Joint Terminal Attack Controllers to Iraqi front lines to direct airstrikes. American support for the Peshmerga included an arrangement providing roughly $415 million for operating costs during their involvement in the operation. Soon after the campaign opened, Islamic State fighters launched an organized assault on Kirkuk on October 20, extending pressure beyond the immediate Mosul front. Ahead of the battle, the group’s leader, Abu Bakr al-Baghdadi, had urged followers in an audio message to hold the city.

Once Iraqi units reached Mosul’s suburbs, the battle shifted from maneuver around the city to combat inside it. Islamic State fighters used tunnels to approach Iraqi troops, emerge behind advancing vehicles and conduct ambushes. Attacks on Humvees cost the Iraqi forces vehicles and casualties. The defenders also used suicide bombers and explosives while concealing positions among civilians and in civilian areas. These tactics slowed an army that had superior numbers and air support, while making it harder for civilians to leave safely. Iraqi units processed people who fled the fighting into displacement camps.

The eastern campaign made steady gains but imposed severe losses on Iraqi Special Operations Forces. On January 15, 2017, the Iraqi Army announced control of 90 percent of Mosul’s eastern bank of the Tigris. Islamic State fighters retreated toward a northern bridge with the aim of reaching the western side. Iraqi security forces seized the bridges linking the city’s two halves, while American forces destroyed ten Islamic State boats on the river to prevent a crossing. By the end of the eastern phase in January, Iraqi forces had defeated the group east of the Tigris. Losses among elite Iraqi troops meant fewer of them were available for the more difficult western assault.

After retaking eastern Mosul, Iraqi forces advanced into western Mosul from the south. They seized the Badush area and its Tigris dam in March 2017 and continued toward the dense western neighborhoods. Fighting there placed ground troops, Islamic State positions and civilians in close proximity. On March 17, an attack in the Al-Jadida neighborhood killed 107 civilians. A U.S. Defense Department investigation found that the airstrike hit its intended military target and that Islamic State fighters detonated planted explosives afterward, causing the fatal secondary explosion. Investigators found that pro-government forces had not known the explosives were present.

By late May, Iraqi forces had pushed the Islamic State into a small part of western Mosul. On May 27, they attacked the Old City and three adjoining areas near the Tigris’s western bank. Iraqi estimates on May 28 put less than 10 percent of the city’s area under Islamic State control. The Old City had become the group’s last major stronghold in Mosul. Iraqi forces distributed leaflets urging its residents to evacuate before the final assault, but movement out of the combat zone remained difficult while defenders fought from crowded streets and buildings.

In early June, fighting concentrated in Al-Zanjili, north of the Old City, where Iraqi forces had retaken about one-third of the neighborhood. They captured additional western districts as the battle entered its final stage. In the Old City, Islamic State fighters relied on snipers, suicide bombers and car bombs to resist the advance. The terrain narrowed the attackers’ options, and the prolonged assault destroyed parts of Mosul’s historic center. Iraqi forces completed the defeat of the Islamic State in Mosul in July 2017, ending nearly nine months of campaigning that had begun on the city’s outskirts.

Terrorist tactics and propaganda

The Islamic State used a combination of prepared defenses and attacks beyond the front line to prolong its hold on Mosul. Tunnels enabled fighters to conceal movement and ambush Iraqi troops. Snipers, suicide bombers and vehicle bombs defended approaches to the Old City. Fighters also hid among civilians and in civilian areas. The group claimed 501 suicide bombings in and around Mosul between October 2016 and late June 2017. During the first part of 2017, it claimed 265 suicide bombings in Nineveh province, half of its 527 claims across Iraq and Syria. These were the group’s claims, rather than independently established counts of attacks.

Propaganda accompanied the defense. Al-Baghdadi’s message urged Islamic State members to remain in Mosul as the operation opened. After the city fell, the group promoted claims that the battle remained undecided and that its fighters had inflicted heavy Iraqi losses. Those messages could not reverse its territorial defeat. They did, however, accompany continued guerrilla attacks against Iraqi forces and Popular Mobilization Forces elsewhere in Iraq. The loss of a major city reduced the group’s ability to govern territory without ending its capacity for violence.

Outcome

Iraq and the American-led coalition won the battle in July 2017. The victory removed the Islamic State from the city it had held since 2014 and dealt a severe blow to its territorial caliphate before it lost its other controlled areas. In late June, as the final assault continued, al-Abadi had described Mosul’s fall as the end of the group’s state-building project. The distinction between territorial control and an enduring security threat remained consequential: Islamic State operatives continued guerrilla operations after Mosul’s liberation.

The battle’s outcome also affected the balance among its victors. During the final phase, Iranian-backed Popular Mobilization Forces reached the Iraqi-Syrian border west of Sinjar. Their advance gave powerful militias a greater role in territory outside Mosul while Iraq confronted the task of securing the recaptured city. Coalition forces recovered Islamic State computers and hard drives from buildings in Mosul. Information obtained from that material, including names of suspected operatives, was used in international border screening. The military victory thus produced both new security intelligence and unresolved questions about the authority of armed groups within Iraq.

Civilian losses were central to the battle’s outcome. An estimate of 9,000 to 11,000 civilians killed reflects the scale of harm across the campaign, while the Al-Jadida investigation establishes the sequence and findings of one specific incident. The Islamic State’s use of civilians and planted explosives was part of the urban battlefield; the deaths also demanded careful examination of individual attacks. Roughly one million people left Mosul during the campaign. The fighting damaged homes, public services and parts of the Old City, leaving liberation inseparable from a large reconstruction effort.

Aftermath and legacy

After liberation, Iraqi security forces cleared booby traps, mines, weapons and other explosives left by the Islamic State. This work was necessary before residents could safely occupy buildings and streets. Displaced people began returning chiefly to eastern Mosul, which had suffered less damage than the west. By late July 2017, more than 830,000 residents had yet to return home. Destroyed housing created a shortage of places to live, while damage to water infrastructure disrupted supply. Generators provided temporary electricity amid broader problems with the city’s power network.

Recovery extended beyond restoring basic services. Mosul and the nearby Nineveh Plains remained important to Assyrian Christians and other communities whose future depended on security and effective local government. Proposals to reorganize Nineveh province reflected differences among its urban, rural and minority populations, but changing provincial boundaries amid displacement carried its own risks. The continued activity of Islamic State cells and the strength of Iranian-backed militias meant the end of the battle did not resolve questions about protection, representation or Iraqi state authority.

Mosul’s damaged historic fabric became another measure of the city’s recovery. Restoration of the al-Hadba minaret marked a visible step after Islamic State rule and the destructive battle to end it. The campaign also entered popular culture: the film Mosul, released on Netflix on November 26, 2020, depicted the liberation. The battle remains significant both as the defeat of the Islamic State’s last major Iraqi urban stronghold and as an example of the immense civilian and material costs of prolonged warfare inside a populated city.