The last enclave of ISIS’s once vast proto-state has been overrun by US-backed Syrian forces on the banks of the Euphrates river near the village of Baghouz.
"After five years of fighting, we stand here to declare the physical defeat of ISIS and the end of its public challenge over all human being," the Syrian Democratic Forces said on Saturday. "We are proud of what we have achieved as a result of our war against Daesh and Al Qaeda."
The Kurdish-led militia also called on the regime of President Bashar Al Assad to take steps towards reaching a political solution "based on the recognition of elected self-administrations in north-east of Syria" and for Turkey to "stop interfering [in] Syrian internal affairs".
"This critical milestone in the fight against ISIS delivers a crushing strategic blow and underscores the unwavering commitment of our local partners and the global coalition to defeat ISIS," American envoy to the US-led coalition William Roebuck said at a main staging base for the SDF.
"We still have much work to do to achieve an enduring defeat of IS," Mr Roebuck said, using a different acronym for ISIS.
SDF commander in chief General Mazloum Kobani on Saturday appealed for continued assistance until the full eradication of the extremist group, which is likely to return to guerilla warfare.
Earlier on Saturday the SDF spokesman had announced via Twitter that the sliver of land had been fully liberated.
"On this unique day, we commemorate thousands of martyrs whose efforts made the victory possible."
After a weeks-long campaign to route the militants from the final encampment – the culmination of a battle that has lasted years – the SDF on Saturday said that the final ISIS territory had fallen.
The news, coming on the week of the spring festival of Nowruz, will be of particular significance to many Kurds.
Prior to the official SDF announcement President Donald Trump on Friday said the militants no longer controlled any territory in Syria. At the time though the US was still launching airstrikes and sporadic fighting continued on the ground against the group's holdouts.
"It's about time," Mr Trump exclaimed on an airport tarmac in Florida.
The announcement marks a historic moment in the war against the terrorist group that controlled an estimated 34,000 square kilometres of Iraq and Syria and ruled over some 10 million people.
But the international campaign has solely – and at a huge cost – rolled back the militants, first liberating areas of northern Syria with the help of the SDF while Iraqi forces battled to recapture cities lost to the extremists.
Iraq declared a final victory against ISIS in Iraq in December 2017 and now on March 23 the SDF has said the fight against the state that the militant group tried to carve out in Syria is complete.
However, the battle against the ideology and the organisation is far from over.
In Iraq and Syria, ISIS supporters and terror cells are still operating. Killings, assassinations and targeted killings are not uncommon in many areas where the group used to operate.
There is also the lingering question of what to do with the tens of thousands who once were members or supported ISIS.
From the last pocket around Baghouz alone, tens of thousands of fighters, their families and supporters have surrendered to the SDF. Many of the nonmilitary age men have been taken to Al Hol displacement camp several hours from the frontlines. Since the offensive began against the last enclave, the population has swelled from a few thousand to over 65,000 people.
The SDF has said that it cannot indefinitely manage and care for the vast number of ISIS supporters that it is now holding. As well as ideological supporters, it has several thousand captured battle-hardened fighters locked in prison across northern Syria.
In Iraq, hundreds of trials have been held for those accused of supporting the terror group. While rights groups have pointed to the reliance on confessions that may have been extracted under torture and on witness statements without supporting evidence, thousands have been found guilty and many sentenced to death.