ERBIL, Iraq — More than two years ago, a Christian farmer in his 70s named Mosa Zachariah fled his village near Mosul with, as he put it, only the pants he was wearing. He left behind his house, “tons of wheat” and a BMW.

But now that his town, an early target of the Iraqi security forces as they advance on Mosul itself, has been cleared of the Islamic State forces, it is not jubilation he feels, but fear of what awaits him if he tries to return. He wistfully talked about his city’s diversity as something completely unattainable now. “In that time, the Muslims and Christians were like brothers,” he said.

Musab Juma, a Shiite who used to live in the Mosul area, said he would not be going back, either. He relocated to Najaf, in southern Iraq, where he has a food stall and has decorated his home with old photos and antiques from his hometown. Yazidis and Kurds and Shabaks, other minorities that were once vital pieces of Mosul’s human tapestry, have moved on, too. And many Sunni Arabs, who make up most of Mosul’s population, say they will never go home again, even if that is where their parents and grandparents are buried.

Before the Islamic State’s occupation began more than two years ago, Mosul was Iraq’s most diverse city. Its rich culture, stretching back to the ancient Assyrians, and reputation for tolerance made it a vital symbol of an Iraq that could at least aspire to being a unified and whole nation.