Situated in the fertile plains of northern Iraq, Mosul finds itself in close proximity to the site of the legendary Battle of Gaugamela, where over 2,000 years ago Alexander the Great broke through Darius III’s wall of chariots and seized an empire. After surviving countless wars and falling under the control of various kings and empires throughout history, this ancient city located at the heart of the Cradle of Civilization would go on to become the epicenter for manufacturing and mingling cultures in modern Iraq – a thriving metropolis composed of a diverse population of nearly 3 million residents.
It was in Mosul where, in July 2003, Saddam Hussein’s sons Uday and Qusay were killed in a ferocious shootout with U.S. troops. From 2004 to 2008, most of the history-rich city found itself enveloped in the barbaric atavism of al-Qaeda in Iraq (AQI) before having the savage Sunni insurgency repressed by U.S., coalition, and Iraqi forces. However, in December 2011, U.S. troops were withdrawn from the country, and with the Maliki Shiite government in Baghdad continuing with its disastrous sectarian policies, an even darker, rebranded version of AQI was approaching the revered city like a sandstorm on the horizon. By June 2014, hundreds of ISIS’s masked jihadists raced toward Mosul in their machine gun-armed pickup trucks and conquered the city with astonishing ease. From then on Mosul served as the genocidal terrorist army’s crown jewel in the Iraqi half of its self-styled caliphate.
It was obvious that the United States and its allies would not allow Abu Bakr al-Baghdadi to retain control of such a strategic and symbolic prize, but this was the largest city yet that the U.S.-led coalition attempted to wrest from the so-called Caliph’s grasp. In this case, U.S. Central Command would devote considerable firepower supporting an eclectic and often competing array of local forces made up of the battle-tested Kurdish Peshmerga (those who face death), with their dreams of independence; an Iraqi state-sponsored umbrella organization known as the Hashd al-Shabi, or Popular Mobilization Forces (PMF), comprised mainly of Shiite militias with more aligned with the ayatollahs of Iran than the government in Baghdad; and the Iraq Security Forces (ISF), made up of the Iraqi Army, federal police, and an elite skull-mask clad counterterrorism unit known as the Golden Division. Aiding them, furtively embedded on the frontlines as advisers and ground spotters, were the shadow warriors from the U.S. Special Operations Forces.
The significance of Mosul was not lost on ISIS, and the jihadists had long been preparing for this battle. Despite being outnumbered nearly 10 to 1, these Islamic fundamentalist extremists welcomed the fight, reveling in the notion of military fulfillment from Islamic scripture. Based on the authors’ monitoring of ISIS-related channels on the encrypted messaging app Telegram, the jihadists frequently spoke of reenacting the famous “Battle of the Trench.” In that epic battle in 627 AD, the Prophet Muhammad and his followers successfully defended the city of Medina from a massive coalition of Meccan Marauders by terraforming the city and digging massive trenches so as to win a war of attrition. Following this holy template from centuries ago, thousands of fanatical ISIS fighters dug in and systematically turned Mosul into a jihadi fortress.
ISIS fighters dug massive underground tunnels and blasted holes through the walls of houses to create an impressive labyrinth of defense networks; they could strike their foes and then disappear underground or “mouse hole” into neighboring buildings to easily evade pursuit and detection. They also dug trenches through neighborhoods and fields, rigged homes with explosives, laced entire districts with landmines, drafted young children as the “Cubs of the Caliphate” to serve as cannon fodder, and corralled terrified civilians to be used as human shields.
As the pre-dawn air broke on October 16, 2016, Iraqi Prime Minister Haider al-Abadi signaled the start of the “historic operation” aimed at dealing a deathblow to ISIS in Iraq by depriving the terrorists of the city that indisputably lent the greatest credence to its ambitious state-building project. Clad in a military uniform while flanked by senior Iraqi officers, an impassioned al-Abadi boldly stated, “I am announcing today the beginning of these heroic operations to liberate you from the brutality and terrorism of ISIS…The hour has come and the moment of great victory is near." Brett McGurk, U.S. envoy to the Coalition against ISIS, responded to the speech on Twitter, declaring, “We are proud to stand with you in this historic operation.”
However, one cannot understand this battle without first understanding the geography of Mosul. The ancient city is bisected by the Tigris River, effectively splitting it into two sections: East Mosul and West Mosul. There are five bridges linking east and west Mosul over the Tigris River, and ISIS (rightly) assumed the international Coalition would damage the bridges so as to prevent them access to resupply routes. Consequently, the jihadists prepared by making sure there were sufficient weapons stockpiles, ammunition caches, bomb shops, and ground forces on both sides of the river. This meant that the battle would be fought in two separate phases, one on each side of the Tigris – it would begin in the east.
East Mosul: A Modern Battle of the Trench?
As the battle began, an estimated 18,000 Iraqi Army troops departed from their main staging base in Qayyarah, just south of East Mosul. Meanwhile, 10,000 Peshmerga fighters surged westward from the autonomous region of Kurdistan in long armored columns and pressed the jihadi fanatics from the northeast. It is worth noting that Kurdish forces were limited to only seizing areas they planned to garrison over the long term. Lieutenant General Jabbar Yawar, Secretary-General of the Ministry of Peshmerga Affairs, explained that Kurdish forces would not enter Mosul city: “According to the agreement with Baghdad, the Peshmerga will create a [defensive] line, while the Iraqi Army will advance further. We will not go to the center of Mosul…Only the Iraqi Army, federal police and local police will ever enter the city.” When one of the authors, Williams, visited Iraqi Kurdistan in June, a Peshmerga commander explained to him that liberating these areas around Mosul from ISIS was viewed as an opportunity to legitimize their claims to disputed territories.
While much has been made of the PMF’s majority Iranian-backed Shiite militias’ involvement in the operation, they were not actually a major factor in Mosul. Prominent Iraq expert Michael Knights explained to one of the authors, Souza, as the battle was unfolding: “In Mosul city, their role has been minimal, and PMF units inside the city or at its edges are those raised from local micro-minorities (Shabak and Yazidi). Out in western Nineveh, the PMF did long-range desert ops to isolate Mosul from Syria.” As the battle for Mosul reached its final stages, the PMF militias subsequently began to assert themselves further westward to fill out the desert on the Syrian border, sparking tensions with Peshmerga and other local groups. But as far as Mosul went, the Iraqi Security Forces would be leading the effort, and they were rapidly advancing in the plains just east of the city.
As dozens of ISIS-assembled truck bombs – outfitted in defensive shells of armor and loaded with barrels full of explosives – surged across the rural outskirts of Mosul toward ISF and Peshmerga forces, M1 Abrams battle tanks on the front lines were usually able to obliterate them with main-gun rounds long before they could reach their targets. In some cases, if the suicidal drivers managed to evade the fury of the M1 Abrams, U.S.-trained Joint Terminal Attack Controllers (JTACs) acting as the eyes of the Coalition’s air armada on the ground were able to target them and arrange their swift destruction vis-à-vis precision strikes from B-52 bombers.
But the SVBIEDs continued at a relentless pace, and ISIS attempted to mask its movements from Coalition air power by launching surprise operations at night and with the strategic use of smokescreens. ISIS militants went door to door in the scattered villages of eastern Mosul collecting tires to set ablaze and obscure the vision of U.S. aircraft and surveillance drones with drifting clouds of black smoke. Once they were low in tires to burn, the jihadists resorted to sabotaging oil fields and igniting toxic sulfur piles. On October 22, for example, ISIS set the town of Qayyarah’s al-Mishraq sulfur plant alight, forming a noxious cloud of smoke that could be seen by NASA satellites in space. The toxic plumes killed at least two civilians while sending nearly a thousand more – suffering from breathing problems and burning eyes – to seek medical treatment.
However, the outnumbered and outgunned jihadists could do little more than delay the inexorable ISF and Peshmerga advances. By November 1 the Coalition ground forces had reached the gates of East Mosul in the Gogjali district. After having officially breached East Mosul’s rural “security zone,” the Peshmerga ceased offensive operations. While the Iraqi troops would press forward into the city, Peshmerga forces dug in with bulldozers and threw up a new berm, effectively establishing the current Kurdistan Regional Government border with Iraq. The Kurds then shifted focus to securing the sizable town of Bashiqa, northeast of Mosul, and consolidating their territorial gains (Souza interview, Michael Knights, June 2017).
For the ISF, it was at this point when the nature of the battle would inevitably change to grueling house-to-house combat in civilian-packed neighborhoods. Thus Iraq’s renowned Golden Division, widely considered to be the federal Iraq unit with the most reliable offensive capabilities for liberating defended ISIS strongholds, would now enter the battle and lead the charge.
The Golden Division was first organized, equipped, and trained by U.S. Special Forces to help rebuild the Iraqi military after the United States invaded the country in 2003. By the time they entered Mosul the soldiers of the Golden Division were widely heralded as an almost invincible group of “ISIS killers.” Their success on the battlefield, combined with their penchant for wearing ski masks with various skull faces, including that of the Marvel vigilante Punisher, had earned them celebrity status. But ISIS did not fear these skull-mask wearing death squads, and the divinely-inspired jihadists were eager to meet them on the streets of East Mosul.
Upon entering Gogjali in East Mosul (marking the first time Iraqi forces stepped foot in Mosul since 2014) the Golden Division found itself in the terrorists’ crosshairs as jihadi hunter-killer teams were lying in wait. Under cover of rooftop snipers and mortar crews shelling from a distance, four-to-five man squads of ISIS militants attacked the ISF on the front lines with truck-mounted machine guns, AK-47 assault rifles, and rocket-propelled grenades. The fighting in Gogjali was intense, and the crackling of gunfire thundered across the city, but when the smoke cleared the area had largely been secured by the ISF. A commander from Iraq’s Golden Division explained how “[t]here was desperate resistance by the enemy,” but by days end Gogjali had largely been secured, although mines, explosives and some “pockets” of resistance were still being cleared.
As the Iraqi forces continued to advance throughout November and December – passing the horrors of mass graves containing hundreds of beheaded civilians, rotting corpses hanging from lampposts, and crucified bodies displayed on city streets – the jihadists’ sophisticated defense networks began to pose a significant threat. Through the strategic use of underground tunnels and holes smashed between the walls of pancaked buildings, ISIS fighters were able to move like ghosts, easily getting into position to ambush advancing troops and then pivoting to concealed locations. It was not uncommon for Iraqi forces to enter tunnels and find plates of food that were still steaming, indicating just how close they got to the terrorists before they decided to flee.
But as December 2016 rolled into January 2017, and Donald Trump prepared to replace Barack Obama as the United States’ Commander-in-Chief, the stranglehold was seemingly tightening on the desperate band of fanatics trying to defend the gem of the caliphate. By mid-January, Iraqi forces approached the revered Mosul University, where ISIS was prepared to stage its final defense in East Mosul.
The sprawling complex was one of the largest education institutes in Iraq before ISIS transformed it into its main command and control center east of the Tigris River, where it also served as a weapon and drone factory. Now jihadi snipers lurked in classroom windows, and the once alluring campus was turned into a frontline battlefield. Knowing that the area had long been devoid of civilians, the Coalition’s air power blanketed ISIS positions with a rain of satellite and laser-guided munitions. The bombing was coordinated with the earthbound Iraqi forces who subsequently stormed the campus in its aftermath. Despite fierce resistance, it was not long until the ISF managed to liberate Mosul University from ISIS control and began marching toward the Tigris River.
Iraq Prime Minister Abadi declared East Mosul “fully liberated” on January 24, 2017. At this point, after approximately 100 days of grueling battle, U.S. Central Command explained that the United States and its allies had assisted Iraqi forces in Mosul with 558 airstrikes, using 10,115 munitions against ISIS targets. These munitions destroyed at least 151 VBIEDs, 361 buildings/facilities, 140 tunnels, 408 vehicles, 392 bunkers, 24 anti-aircraft artillery (AAA), and 315 artillery/mortar systems. But the ISF understood that the battle to liberate West Mosul on the other side of the Tigris River would likely be even more protracted. It was in West Mosul where the ISIS fanatics were preparing for their last stand, but the Iraqi forces were learning from experience on the ground and welcomed the challenge.
West Mosul: The Death of a Jihadi Dream
On February 19, 2017, Prime Minister Abadi announced the beginning of the offensive to liberate West Mosul. By the time Iraqi forces entered West Mosul, they not only had much more support from U.S. Special Forces on the ground than when the battle began three months earlier, but they had also developed a much better sense of how to neutralize their jihadi opponents’ tactics in house-to-house urban warfare. For example, to defeat the ever-present threat from SVBIEDs, ground troops began calling in “terrain denial requests” to Coalition airpower, which would effectively strike an area and crater roads to inhibit the flow of car bombs. In the case of densely packed neighborhoods where airstrikes would almost certainly result in large numbers of civilian casualties, and where camouflaged SVBIEDs came surging directly at passing ISF columns from garages and covered driveways, ground forces began to “fortify-in-place” by using bulldozers to throw up earth berms and creating roadblocks of their own.
Even though the ISIS militants themselves showed a remarkable ability to endure and adapt in the face of such formidable countermeasures, using off-the-shelf drones equipped with GoPro cameras to fly reconnaissance missions and direct car bombers in real time on alternative routes to their targets, they only enjoyed limited success. At this point in the battle, the ISF had seized a number of walkie-talkies from fleeing ISIS insurgents and divided them among different regiments, allowing them to monitor the jihadists’ radio traffic and keep tabs on their movements. Indeed, after liberating Mosul International Airport on February 24, 2017, with surprisingly little resistance from ISIS, it seemed things were going smoother than expected in West Mosul. However, the ISF’s early success west of the Tigris belied the arduous battle that lay ahead.
For all of their remarkable progress, the Coalition was about to suffer a widely documented setback. On March 17, 2017, as the ISF were advancing in the Jidideh section of West Mosul, two ISIS snipers began firing at them from atop a nearby building. JTAC spotters on the ground contacted the Erbil-based command center and requested air assistance, which was quickly provided in the form of a GBU-38 satellite guided munition dropped from an American aircraft. The aim was to simply take out the snipers on the top floor, but, tragically, the entire building collapsed and killed over 100 Iraqi civilians. While ISIS and some nearby residents claimed the airstrike alone destroyed the building, a Pentagon investigation concluded that ISIS deliberately staged about 1,000 pounds of secondary explosives in and around the building, which were triggered by the GBU-38 and ultimately caused it to collapse. According to the investigation, an analysis of the building debris found explosive residues that are common in ISIS-made bombs, including nitroglycerin but are not used in the GBU-38.
As human rights organizations continued to express profound concern over the escalating civilian death toll in Mosul, U.S. Secretary of Defense James Mattis publicly addressed the issue. Speaking on CBS’s Face the Nation on May 28, 2017, Secretary Mattis explained that the United States would “do everything humanly possible” to prevent such casualties from occurring again. But he also described civilian casualties as a “fact of life in this sort of situation” and expressed his intention to “annihilate” the ISIS jihadists.
By this time, the Iraqi ground forces had finally reached Mosul’s Old City, where ISIS grew desperate. As defeat seemed inevitable and the ISIS terror state in the plains of northern Iraq continued to collapse, many of the jihadi fanatics began selling off their last possessions, including pagan Yazidi sex slaves, with hopes of making enough money to escape to neighboring Turkey. When one of the authors, Williams, visited the frontlines near Mosul in early June, he participated in delicate negotiations (through a smuggler) for Yazidi parents to buy back their 14-year-old daughter Fayza Murad from an ISIS captor for $17,000.
But not all of the ISIS fighters wanted to escape, and the few hundred who remained in the Old City pledged to fight to the death. At this point, after having used up most of its supply of suicide bombers, ISIS began to rely more heavily on embedding itself within the civilian population to use them as human shields. In some cases, ISIS fighters would exit buildings holding crying babies over their heads and run across the street, knowing it would protect them from airstrikes. The use of such barbaric tactics allowed ISIS fighters to bog down the ISF in the maze of narrow streets and alleyways in the Old City. However, by early June the sense of urgency was palpable, and Iraqi forces ramped up the operation considerably by launching a “thunder run” through the neighborhoods of Shifa, Zinjili, and Saha. These three areas were seen as the last barriers that separated Iraqi forces from ISIS’s “last bastion” around the ancient al-Nuri mosque.
In mid-June, after over 8 months of grinding urban warfare, the Iraqi forces were just 200 meters from the al-Nuri Mosque – the symbolic heart of ISIS’s crumbling caliphate, where the infamous Black Banner had been hoisted atop its distinctive leaning minaret (nicknamed Al-Hadba, or "the hunchback") in the fateful summer of 2014. The mosque had played a starring role in ISIS propaganda, its symbolism not lost on al-Baghdadi, as he likely hid somewhere near the Iraqi-Syrian border in safety.
It was in the al-Nuri Mosque where, on July 4, 2014, Baghdadi dressed in all black attire that symbolized the fabled Abbasid dynasty, mounted the minbar (pulpit), and gave a filmed sermon (the only time he ever appeared on camera). It was here that the man with a $10 million U.S. bounty on his head brazenly proclaimed to all Sunni Muslims, “I am your leader who presides over you” and called on them to “obey” him and fight jihad for the sake of Allah. This call on the faithful to help reconstruct the Abbasid caliphate of the thirteenth century was answered by thousands of jihadists who viewed al-Baghdadi as the literal “Shadow of God” on earth. Now, three years later, Baghdadi watched as his enemies closed in on that very shrine that was so replete with symbolism.
But on June 22, 2017, ISIS terrorists decided they would rather flatten the mosque themselves than concede it to their “infidel” opponents. Hisham al-Hashimi, a security expert who advises the Iraqi government on counterterrorism matters, explained the rationale for this act of “culturecide” to the Guardian: “They blew it up because they did not want the place they announced the caliphate from to be the place where the Iraqi military announces its victory over them.” As the ancient minaret that had graced the Nineveh skyline since the twefth century fell into a heap of rubble, so, too, did the dreams and aspirations of thousands of Sunni jihadists who boldly dared to reconstruct the fabled caliphate that fell to the Mongols in 1258.
Finally, on July 8, 2017, Prime Minister Abadi arrived in West Mosul and formally announced the city’s liberation. Dressed in an all black military uniform, similar to those worn by the Golden Division, Abadi congratulated “the heroic fighters and the Iraqi people in achieving this great victory." After 266 days of what was arguably the largest high-intensity urban battle seen since WWII, Abadi’s announcement prompted widespread jubilance – national fervor quickly pervaded the city. Iraqi soldiers blasted music and fired their machine guns into the air while civilians waved Iraqi flags and danced on the bomb-blackened, rubble-strewn streets.
The Aftermath of Battle
Despite Abadi’s declaration of victory in Mosul, there is still much work to be done. ISIS fought ferociously to defend every foot of soil in Mosul, and the Coalition’s victory caused great physical and material damage: swaths of the city reduced to rubble, thousands of civilians perished, and nearly one million people were driven from their homes. According to the United Nations, initial repairs to the city’s basic infrastructure are expected to cost more than $1 billion.
To compound matters, the constellation of forces that worked together to liberate Mosul, united only by their collective antipathy toward the ISIS caliphate, will face new challenges as they compete for influence and territory. The Kurds made significant territorial gains fighting ISIS and have announced a September 25 memorandum, calling for an independent state. This, while Iranian-backed Shiite militias from the PMF are vying for control along the Iraqi-Syrian border. The government in Baghdad is yet to put forward a competent reconstruction plan for Mosul. ISIS sleeper cells lay in wait, hoping Prime Minister Abadi will repeat the mistakes of his predecessor when AQI was repressed. All while ISIS still controls some territories in the Anbar province, Tal Afar, and in the Sunni-dominated town of Hawijah, which lies between Baghdad and Mosul.
However, ISIS’s defeat in Mosul is nevertheless reason to celebrate. One eyewitness summed up the battle as he walked past slain bodies of ISIS militants rotting in the streets: “They deceived you and promised you heaven and virgins but now you’re just lying here, dead, and soon you will be thrown into the garbage.” Thus a mere three years after ISIS surprised the world by blazing across the burning desert in machine gun-armed pickup trucks and boldly seized Iraq’s second largest city, the very same jihadists’ bodies lay in the rubble of what was their greatest possession. While ISIS will almost certainly return to its Sunni insurgent roots and operate as a virtual government in exile with global influence, its days of operating as a proto-state are nearly over. The Iraqi half of ISIS’s self-styled caliphate has been destroyed, and the battle for its capital in the Syrian city of Raqqa is already in progress.
Robert T. Souza is a Middle East Research Analyst at the Center for the Study of Targeted Killing, where he focuses mainly on counterterrorism in Iraq and Syria. He is also an Assistant Managing Editor for the Fellowship Program at Young Professionals in Foreign Policy in Washington, DC.
Brian Glyn Williams is a Full Professor of Islamic History at the University of Massachusetts Dartmouth and formerly taught at the University of London. He is the author of Counter Jihad: The American Military Experience in Afghanistan, Iraq, and Syria. Brian previously worked for the CIA’s Counterterrorism Center in Afghanistan and the U.S. Army’s information operations in Kabul.