IRBIL (Iraq) • The documents in the Islamic State in Iraq and Syria (ISIS) file hinted at signs of rebellion within the ranks of its foreign fighters. A Belgian militant had a medical note saying he had back pain and would not join the battle. A fighter from France claimed he wanted to leave Iraq to carry out a suicide attack at home. Several requested transfers to Syria. Others just simply refused to fight.

The documents on 14 "problem" fighters from the Tariq Bin Ziyad battalion - made up largely of foreigners - were found by Iraqi forces after they took over an ISIS base in a neighbourhood in Mosul last month.

At its peak, ISIS drew thousands of recruits monthly and controlled about a third of Iraq's territory, and foreigners who poured in from dozens of countries have been characterised as the most die-hard fighters.

But the group has steadily lost ground and appeal.

The militants are now besieged in the western half of Mosul, once the biggest city ISIS controlled and the heart of its self-proclaimed cali- phate. But the group's losses have triggered concerns in Europe that disillusioned fighters might find their way home.

"He doesn't want to fight, wants to return to France," said the notes on a 24-year-old listed as a French resident of Algerian descent. "Claims his will is a martyrdom operation in France. Claims sick but doesn't have a medical report."

He was one of five fighters in the file listed as having French residency, or as originally from France. More citizens from France have joined ISIS than from any other country in Europe since 2011, when Syria's uprising against President Bashar al-Assad turned violent and fuelled the rise of extremist groups.

The French government reported a sharp decrease in the number of its citizens travelling to Syria and Iraq to join the group in the first half of last year, but said that nearly 700 still remain there, including 275 women and 17 minors.

The forms in the file are marked with the year 2015, but appear to have been filled out later as they specify the dates that some of the militants joined, which stretch into last year. In addition to each militant's name, country of origin, country of residency, date of birth, blood type and weapons specialities, the documents list the number of wives, children and "slave girls" each had. A photo is also included.

It was not possible to verify the personal information, but Iraqi officers who found the file said they believe it is genuine.

Of the more than 4,000 foreign fighters who had left European Union nations for Iraq and Syria, around a third have returned, according to a report from The Hague-based International Centre for Counter-Terrorism. About 14 per cent are confirmed dead, while the rest remain overseas or their whereabouts are unknown.

"People say that they are the most motivated, but there are plenty of foreign fighters that went and found that the ISIS experience wasn't what they thought it would be; they thought it would be a great adventure," said analyst Aymenn al-Timimi, who has compiled an online database of ISIS documents, some of which indicate similar issues of morale.

ISIS keeps meticulous records, leaving clues to its inner workings as fighters are ejected from territory.

Iraqi counterterrorism forces discovered the documents in a house in Mosul's al-Andalus neighbourhood that was an administrative base for the Tariq Bin Ziyad battalion. The militants were seen removing documents and computers from the building, according to neighbours, before they set fire to the building as Iraqi forces retook the area, said Lieutenant-Colonel Muhanad al-Tamimi, whose unit found the documents unscathed in a desk drawer.

"Those foreign fighters are the most furious fighters we ever fought against," he said. "When those fighters refuse to fight, it means that they've realised this organisation is fake Islam and not the one they came for."

Lieutenant-General Abdul Ghani al-Assadi, commander of Iraq's counterterrorism forces, said there are many foreign fighters in Mosul, and foreign suicide bombers have been responsible for many of the 350 car bombs launched towards their lines.

In one ISIS headquarters in the Dhubat neighbourhood of Mosul, his forces found a stash of passports - 16 Russian and four French. There were also 20 blank Iraqi passports taken from Mosul's passport department, he said, speculating that the militants are forging them to leave the country.

WASHINGTON POST