Caliphate defeated but IS remains a threat
A US-backed alliance of Syrian fighters has announced that the jihadist group Islamic State (IS) has lost the last pocket of territory in Syria it controlled, bringing a formal end to the "caliphate" it proclaimed in 2014.
IS once controlled 88,000 sq km (34,000 sq miles) of territory stretching from western Syria to eastern Iraq. It imposed its brutal rule on almost eight million people, generating billions of dollars in revenue from oil, extortion, robbery and kidnapping.
Despite the demise of its physical caliphate, IS remains a battle-hardened and well-disciplined force whose "enduring defeat" is not assured.
The head of the US military's Central Command, Gen Joseph Votel, said in February that it was necessary to maintain "a vigilant offensive against the now largely dispersed and disaggregated [IS] that retains leaders, fighters, facilitators, resources and the profane ideology that fuels their efforts".
And if pressure on the group is not sustained, , military officials told the US Department of Defense Office of the Inspector General in January.
Such warnings appeared to persuade Mr Trump not to withdraw all of the 2,000 US troops from Syria, as he had promised in an announcement in December 2018. That plan prompted the resignation of Defence Secretary Jim Mattis and alarmed allies in the Global Coalition to Defeat IS.
, 200 of which would be based at the al-Tanf outpost, at the intersection of the Syrian, Jordanian and Iraqi borders.
In Iraq, where the government declared victory in December 2017, , UN Secretary General António Guterres said in a report to the Security Council released in February.
"It is in a phase of transition, adaptation and consolidation. It is organising cells at the provincial level, replicating the key leadership functions," he added.
IS militants are active in rural areas with remote, rugged terrain that gives them freedom to move and plan attacks. These include the deserts of Anbar and Nineveh provinces, and the mountains that straddle Kirkuk, Salah al-Din and Diyala provinces.