Growing numbers of Western extremists are deserting DAESH and returning to countries like France, where security services are trying to sort genuine repenters from terror suspects, experts say.
DAESH, which is losing ground on several fronts in Syria and Iraq, is also battling to prevent some of the thousands of foreign volunteers who have joined its ranks since 2014 giving up the fight and going home.
"They sense that we have entered the final stage. Many are starting to send us messages to know how they can return," France's national intelligence coordinator, Didier Le Bret, told AFP. "We know that some have been killed while trying to flee," he added.
Slipping past the extremists is no easy task, making Western security services wary of returning extremists. "We worry when we get someone back. How do you know whether he is sincere or on a mission?" Le Bret said.
Patrick Calvar, head of the domestic intelligence agency DGSI told the National Assembly, or lower house of parliament, in mid-May that 244 people had returned to France from Syria and Iraq. "We're seeing more and more (expressions) of intention to return home," he told lawmakers. But many of those who wanted to defect were "prevented by DAESH policy, which considers those who want to leave Syria as traitors to be immediately executed," he said.
In January 2014, a study by the International Centre for the Study of Radicalisation (ICSR) at King's College London set up a database of returning extremists to try to understand their motivations. The list currently runs to 60 names.
The ICSR gave various reasons for the growing disenchantment among DAESH recruits. "The defectors' reasons for leaving may be as complex as the reasons they joined," ICSR Director Peter Neumann wrote in a report in September. "Not everyone has become a fervent supporter of liberal democracy. Some may have committed crimes."
Neumann said the main complaints that emerged from the testimonies of the returnees are "DAESH is involved in brutality and atrocities against Muslims," "DAESH is corrupt and un-Islamic" and "life under DAESH is harsh and disappointing."
Shiraz Maher, one of the researchers who interviewed the deserters, told AFP that "most" of the returning fighters insisted "I didn't come [to Syria] for that."
The losses sustained by DAESH in Syria and Iraq in recent weeks may also spur the homeward movement. Scores of DAESH fighters have been killed on various fronts, according to monitors.
Life in DAESH strongholds like the Syrian city of Raqqa is often a far cry from the utopian visions of a pure Islamic society that lured some foreign combatants.
Heady dreams of adventure, comradeship and glory on the battlefield founder on a daily diet of grinding hardship, wanton barbarity and constant fear - of DAESH itself, bombardments by its adversaries or both. Shiraz recalled: "One told me they think nothing of bringing down buildings with women and children inside, just to kill one person. It's just slaughter."
Some of the returnees also complain of discrimination by DAESH commanders on the basis of country of origin. An Indian who went to fight was relegated to the most menial of tasks. "They made me clean the toilets," he said.
Last month, the Obama administration's diplomatic point man in the fight against DAESH said that the extremists have been losing control over territory. Brett McGurk said DAESH has suffered recent military setbacks and lost territory in both Iraq and Syria and added the group is on the defensive and that "this perverse caliphate is shrinking."
On May 22-23, Iraqi forces launched an operation to retake Fallujah, which lies only 50 kilometers from Baghdad. Iraq's elite counter-terrorism service moved to within three kilometers of central Fallujah Friday and consolidated positions in the south of the city, the operation's commander said.
DAESH has tried to leave the besieged city by blending in with the flow of displaced civilians who are attempting to escape by crossing the Euphrates south of Fallujah. According to the Norwegian Refugee Council that runs displaced camps in Amriyat al-Fallujah, south of Fallujah, more than 20,000 people have fled the fighting over the past three weeks.