Explained: Islamic State and Syria
Earlier this week, US secretary of state Antony Blinken warned that the power vacuum left by the toppling of Bashar al Assad in Syria could lead to a resurgence of the so-called Islamic State terror group in the country.
Often called ISIS, ISIL, or the pejorative Daesh, Islamic State has spent the past few years trying to rebuild, aiming to emulate the height of its power from 2014-2017.
The militants were based in the Syrian city of Raqqa and the Iraqi city of Mosul, holding sway over a wide area in both countries.
The group originally took advantage of the civil war in Syria and took parts of the north of the country, where it enforced its extreme interpretation of Islamic law on the population.
But the group collapsed in Iraq, where it once had a base only a 30-minute drive from Baghdad, and in Syria after a sustained military campaign by a US-led coalition.
Tens of thousands of IS fighters and their families captured during the five-year-long battle are now in prisons run by Kurdish authorities.
Other fighters have since sought refuge in the hinterlands of the two fractured countries, scattered in autonomous cells.
Their leadership is clandestine and its overall size is hard to quantify, but the UN estimates it at 10,000 in its heartlands.
The US National Counterterrorism Center has said the threat posed by IS and another militant group al Qaeda "is at a low point with the suppression of the most dangerous elements".
But it went on to warn half of IS's branches are now active in insurgencies across Africa and "may be poised for further expansion".
Although Islamic State was almost completely eradicated in Syria by the US in 2019, it still has some presence in parts of the country.
The US Army has kept around 900 troops inside Syria to suppress any activity, with IS attacks becoming more frequent since 2023.
Most recently, the group claimed responsibility for an attack on a Russian concert hall in March - killing 143 people - and a suspect behind the plot to attack a Taylor Swift concert in Austria earlier this year vowed allegiance to the group's leader.
Since Assad's fall, the US and Israel has struck several chemical weapons compounds and other ammunition sites in order to stop such munitions falling into the hands of Islamist extremists that could lead an Islamic State revival.
But it remains unclear whether the group could muster the strength that saw it rise to prominence in the previous decade.
If you want to read more about ISIS, our special correspondent Alex Crawford filed this report on their attempts to rebuild earlier this year, which you can read here.
And out security and defence editor Deborah Haynes has also written up a story on experts warning the evolving crisis creates the potential for a new wave of terrorism to emerge.
Read that here.