By early July, ISIS fighters had killed thousands of government troops and police officers, and Iraqi commanders were under enormous pressure to finish the battle. The next few weeks were a bloodbath. ISIS fighters who surrendered were executed on the spot. Iraqi security forces filmed themselves hurling captives off a cliff, then shooting them as they lay dying on the rocks below. Helicopters buzzed the Tigris, bombing people as they tried to swim across. The troops assumed that anyone still living in the Old City sided with the Islamic State. For the rest of the month, corpses bobbed downstream, dressed in civilian clothes. “We killed them all—Daesh, men, women, and children,” an Iraqi Army officer told a Middle Eastern news site, using the Arabic acronym for ISIS. As he spoke, his colleagues dragged a suspect through the streets by a rope tied around his neck. “We are doing the same thing as ISIS. People went down to the river to get water, because they were dying of thirst, and we killed them.”

When the battle was over, soldiers used construction equipment to shovel rubble into the entrances of ISIS tunnels—ostensibly to suffocate any remaining jihadis, but also to mingle corpses and concrete, thereby obscuring the scale of the atrocities. As late as March of this year, journalists were still finding the bodies of women and children on the riverbanks, blindfolded, with their hands tied behind their backs and bullet holes in their skulls.

A year and a half after Iraq declared victory, the Old City is in ruins. Sunlight gleams through bullet holes in tin garage doors. Massive blocks of concrete dangle from broken roofs. The floors of apartment buildings remain as they fell, in layers, having crushed whatever was between them. The U.N. estimates that the battle for Mosul has left behind around ten million tons of rubble. Some stone structures have landed at odd angles, to disorienting effect, as if gravity were pulling in every direction. There are burned-out power lines, and staircases to nowhere. It is completely silent. Near the site of an old post office, there is a single intact traffic light. It changes every thirty seconds, for no one. Every few feet you catch the smell of desiccated corpses. Also inescapable is the scale of history, obliterated. Many of the buildings were continuously inhabited from the seventh century until the second week of July, 2017. To walk through the Old City is to tread on its final generations’ graves.

Shortly after the battle ended, Mohammad returned to his job in the civil defense. Every day, locals lined up outside a temporary fire station in West Mosul and asked for help retrieving the bodies of their relatives. “We recorded their names and gave them a date,” he recalled. “And when their date came they would come with us to the Old City and show us the house that had been hit by an air strike, and we would dig until we could take out the body.”

The coalition has acknowledged a civilian death toll in the low hundreds. But the West Mosul civil defense has retrieved thousands of corpses from the Old City. Last December, the Associated Press obtained a list of nearly ten thousand civilians whose bodies had been registered at the local morgue. Most had been crushed to death by falling concrete; for others, the cause of death had been entered into the morgue’s database simply as “blown to pieces.” (Thomas Veale, a U.S. Army colonel and a spokesman for the coalition, told the A.P. that it was “irresponsible” to draw attention to civilian casualties in West Mosul. If not for the coalition’s campaign, he said, Iraqis would have suffered years of “needless death and mutilation” at the hands of “terrorists who lack any ethical or moral standards.”)

“All of them are civilians,” Mohammad said. “When we find unknown bodies, we leave them behind,” because there would be no way to apply for a death certificate or to return a corpse to its family for burial. “Sometimes people come here and tell us that they have dead relatives in the Old City, but we know that they are not from the Old City,” Mohammad said. “They are from Qayyarah or Shirqat,” towns where the Islamic State had more support. When that happens, civil-defense workers infer an ISIS link and refuse to retrieve the corpse.

The skeletons in the rubble have not been picked clean by animals, or bleached white by the sun. There are fingernails and yellow teeth and dusty clumps of hair. Bone fragments line the roads, amid scraps of fabric and leather and glass. Near the river, I saw a torso dangling loosely from a mess of twisted rebar—swaying hands, fractured skull. Blackened ligaments drooped from the arms. “Daesh,” a stranger said to me, smoking a cigarette, pointing at the corpse. He kept moving.

Nearby, I met Thenoon Younnes Abdullah. He waved, and carefully wound his way down a three-story pile of rubble—the site of his former home—with his ten-year-old son. The family had returned to salvage whatever they could. Everything of any value had already been looted, but they rescued a broken generator, and tied it to the back of their car.

Abdullah told me that, after the battle, his cousins were the first in his family to return to the Old City; as soon as they opened their door, they were blown apart by I.E.D.s. Months later, when Abdullah arrived, he found his own house in ruins, and several dead ISIS fighters inside. He also found Alaa’s mother’s corpse; she had stayed behind, too frail to run away.

Abdullah led me up the hill of tangled metal and concrete, and we entered his house by ducking under a staircase, through a hole in the bathroom wall. On the floor of the dining room were three stains, where fluids had leaked out as the bodies decomposed. Abdullah’s brother died across the street, but his body hasn’t been found.

It was difficult to move. The floor was littered with debris, but I noticed transistors, ball bearings, and other bomb-making materials scattered about. Then, on my way out, my foot knocked over a concrete block and uncovered an I.E.D. I stopped, and noticed two other unexploded bombs a few feet away, as well as four detonators. We climbed back out through the hole in the bathroom wall, and came down the hill, past an ISIS corpse in rotting leather sandals.

Reconstruction in the Old City will cost billions of dollars, according to the U.N., but, aside from the exorbitant cost, I had the impression that the Iraqi government has been content to leave it in ruins, as a kind of punishment. Abdullah told me that he had seen no evidence of institutional cleanup—only posters from N.G.O.s, warning about the perils of walking in areas filled with unexploded ordnance, which still regularly kills people in the Old City.

Abdullah and his family piled into their car and headed to another part of the city, where they were staying in an abandoned, mostly destroyed building. He navigated by peering through a hole in the windshield, caused by shelling more than a year earlier.