The Syrian Democratic Forces has declared victory over Islamic State in Syria, ending the group’s self-declared caliphate that once stretched across the country and neighboring Iraq.

“Syrian Democratic Forces declare total elimination of so-called caliphate and %100 territorial defeat of ISIS. On this unique day, we commemorate thousands of martyrs whose efforts made the victory possible. #SDFDefeatedISIS,” SDF spokesperson Mustafa Bali tweeted on Saturday, March 23.

Syrian Democratic Forces declare total elimination of so-called caliphate and %100 territorial defeat of ISIS. On this unique day, we commemorate thousands of martyrs whose efforts made the victory possible. #SDFDefeatedISIS — Mustafa Bali (@mustefabali) March 23, 2019

In a statement Saturday, the SDF said 11,000 fighters were killed and 21,000 seriously wounded in the fight.

“On this occasion we cannot but remember those heroes and pay tribute to the memory of the martyrs and wish the urgent recovery of their wounds, without their sacrifices we would not granted this victory,” the SDF General Command said.

Also among the dead are foreign forces from the U.S.-backed Coalition, including American service members killed in a January suicide bomb attack in Manbij that was later claimed by ISIS, and dozens of international volunteers who fought with the SDF.

“We affirm that our war against Da’ash terrorism will continue until full victory is achieved and the total elimination of its existence,” the statement added, using an Arabic acronym for Islamic State.

“At the same time, we announce to the world public opinion the beginning of a new phase in the fight against terrorists, and this through the continuation of precise military and security campaigns in coordination with the international coalition forces with the aim of completely eliminating” ISIS sleeper cells.

The SDF launched the operation against the last ISIS redoubt in February but slowed down the offensive to protect civilians while tens of thousands of people fled the enclave – along with the families of ISIS fighters.

On Thursday, Bali said the force was still searching for fighters hidden in Baghuz.

After rising to power in 2014, ISIS once controlled a territory in Iraq and Syria as large as the United Kingdom, but that land has been recaptured by collective Iraqi security forces and the Syrian Democratic Forces in Syria, backed by a 79-member international Coalition led by the United States.

The SDF recaptured the group’s de facto capital Raqqa in October 2017 and former Iraqi Prime Minister Haider al-Abadi declared victory over ISIS in Iraq in December 2017 after a harrowing three-year fight.

The victory declaration may lead to more questions than answers, such as the whereabouts of ISIS leader Abu Bakr al-Baghdadi, the future of U.S. forces in Syria, and whether Turkey will launch more operations against the SDF, whose core force the People’s Protection Units (YPG) it considers a terrorist group.

Although the loss of Baghuz ends ISIS’s control of territory, the group retains a presence in Syria, mainly in the southern Badia desert, and cells that periodically carry out attacks in Iraq. It is unclear how many ISIS fighters fled the shrinking territory and are now capable of waging an insurgency in the region.

Western hostages, including the British journalist John Cantlie, remain missing, and millions of refugees from Syria are still unable or unwilling to return home while President Bashar al-Assad remains in power with the backing of Russia.

Also uncertain is the future for thousands of suspected ISIS captives in SDF custody or those facing trial – and death sentences – in Iraq, as well as foreign fighters whose home countries are reluctant to repatriate and try them for crimes against the Iraqi and Syrian people.