BEIRUT, Lebanon — The Syrian military and its allies have begun a long, slow and violent campaign to recapture the last province in the country still under opposition control, where the government has gradually cornered rebels, extremists and civilians alike.

A victory in Idlib Province, in Syria’s northwest, would help the country’s president, Bashar al-Assad, and his allies Russia and Iran consolidate what increasingly looks like an assured victory in an eight-year-old civil war. But it would almost certainly come at a high cost in life and property.

Last Wednesday, with airstrikes splitting open the Syrian countryside near their home, the Esmail family was selling everything they could not carry: their carpets, their washing machine, their refrigerator.

On Thursday, they packed up the rest. On Friday, they searched frantically for shelter outside the danger zone, knowing not where to flee, but only that they must.