With the decision by the United States to withdraw from its positions in northern Syria, and Turkish forces moving in, the fate of thousands of suspected Islamic State detainees remains unclear.
The detainees and their families - held by Kurdish-led forces - include foreigners from various parts of the world.
The US has called on foreign states to repatriate their nationals, accusing European nations of refusing to do so.
The US has pressed France, Germany, and other European nations to take back captured IS fighters, but they did not want them and refused.
So, how many foreign nationals are being held by Kurdish-led Syrian Democratic Forces (SDF) and have any countries taken them back?
The families of suspected IS militants are being held at a number of camps for displaced people in northern Syria.
By far the largest is at al-Hol. It is housing almost 70,000 people, more than 94% of them women and children, of whom 11,000 are foreign nationals.
Additionally, the SDF says some 12,000 suspected IS fighters are held in seven prisons in north-east Syria, of whom about 4,000 are estimated to be foreigners (that is, neither Syrian nor Iraqi).
A US government report published in August has a lower figure for foreign adult combatants held in northern Syria - 2,000, originating from 50 countries.
Of these, about 800 are from European nations while the rest are from the Middle East, north Africa or Asia.
To put that into context, a study last year by King's College's International Centre for the Study of Radicalisation estimated more than 41,000 foreign nationals had joined IS in Iraq and Syria between April 2013 and June 2018.
Has anyone taken back their nationals?
The United Nations has said countries should take responsibility for their own citizens unless they are to be prosecuted in Syria in accordance with international standards.
Many countries have been reluctant to do so, worried about public opinion and the legal challenges of dealing with citizens who joined IS.
Human Rights Watch has described government-facilitated repatriations of foreign nationals as "piecemeal."
It says more than 1,200 foreign nationals - mainly children - have been repatriated from both Syria and Iraq to Kazakhstan, Uzbekistan, Tajikistan, Russia, Kosovo, and Turkey.
But other nations have taken back only very small numbers:
- France: 18 children
- US: 16 adults and children
- Germany: fewer than 10
- Australia: eight children
- Sweden: seven children
- Norway: five children
In some cases, foreign nationals have been transferred to Iraqi jurisdiction and tried in that country's courts. Earlier this year, four Frenchmen were sentenced to death in Iraq in a judicial process heavily criticised at the time.
Some foreign governments have revoked citizenship to prevent the return of suspected IS members - for example in the case of Shamima Begum, from the UK, who is being held at an SDF-run camp in Syria.
Far larger numbers of foreigners who joined IS are likely to have made their own way home before Kurdish-led forces captured the jihadists' last pocket of territory in March.
The International Centre for the Study of Radicalisation estimates the numbers globally to be between 7,712 and 8,202.
This includes both voluntary returns as well as government-facilitated repatriations, although it adds the latter are likely to be minimal.
Joana Cook and Gina Vale, co-authors of the study, told BBC News: "Many governments appear more willing to facilitate the return of minors, particularly vulnerable ones like orphans, than the return of adult detainees."