MOSUL, Iraq—It was a surprising sight. The customers standing in Haj Hamdoun’s store in central Mosul watched as a masked child came into the shop, bought what he wanted without saying a word and then left again, carrying a bag containing candies and milk in one hand and a heavy machine gun, which was just about as big as him, in the other.

This was Abdullah, who appears to be the city’s youngest volunteer with the Sunni extremist group, the Islamic State of Iraq and al-Sham, or ISIS, that took control of Mosul over two weeks ago.

Abdullah is not yet 11 years old. But his older brother and his father, who was a senior member of ISIS, were killed in fighting between the group and Iraqi security forces in 2013. That’s why Abdullah joined ISIS, although he is far from the only child in its ranks.

The storeowner, Hamdoun, says he has actually grown used to seeing Abdullah wandering around, carrying his big gun with both pride and difficulty. He has also seen the boy on guard duty together with other ISIS fighters in front of the new ISIS headquarters in Mosul, which originally was the home of a government official.

A curious bystander wanted to start a conversation with Abdullah. “I have a son your age, but he’s not eager to carry arms,” the man said. “He spends most of his time on the computer.”

A tall, overweight gunman, who seemed to be responsible for the child, answered on Abdullah’s behalf. “Our children don’t waste time on electronic games or on watching cartoons,” he said. “They have a dream and their dream is to establish an Islamic state.”

The gunman patted Abdullah’s shoulder. “We have a lot of hope for Abdullah and other children his age,” the gunman continued. “We believe they will conquer all of Iraq and Persia and that they will liberate Jerusalem.”

Abdullah may be the youngest volunteer with ISIS but other children and teenagers also have become enthusiastic about bearing arms for the extremist group in Mosul. As soon as ISIS arrived here, it began to attract new members, aged anywhere between 10 and 30, who were drawn to the glamour of the group’s obvious power and the adventure of joining such a well-armed gang.

Although estimates vary, the number of ISIS gunmen who eventually took control of Mosul was certainly not more than 4,000. So they need more recruits, both to control the territories they have and to join the fight on other fronts within Iraq.

This appetite to join ISIS has become a source of concern for Mosul’s families. Locals are only too well aware that many of those now controlling their city are young people who only volunteered to join ISIS several days ago, and that many of them are new to the weapons they carry.

Locals also know that ISIS needs more fighters in places like Tikrit, Anbar, Diyala and toward Kirkuk.

Despite that obvious need for more recruits, ISIS does have certain rules for membership, and the image of exclusivity is part of its mystique.

Firstly, the volunteers must be willing to obey their ISIS leader even if his orders may result in their death. Those who do not obey orders or those who retreat will be considered “apostates,” for which the penalty is death.

Additionally, any volunteer who wants to join must be recommended personally by another member of ISIS, who must have belonged to the organization for not less than two years. The volunteer must have good conduct and must be committed to the teachings of Islamic law, as defined by ISIS interpretation of the Sunni branch of the religion. And if the volunteer was formerly a member of the state security forces, he can only join a year after declaring repentance. ISIS offers any member of local security forces or police a pardon in return for declaring repentance at one of several mosques set up for the purpose.

Once volunteers are accepted, they are given religious lessons in accordance with the strict Salafist doctrine, trained in the use of weapons, and they also undergo physical training.

But there are other obstacles that young Mosul men who want to join ISIS may also have to overcome: among them, their mothers.

There was no way Saad was going to let her boy enlist. She said that although a neighbor tried to calm her by telling her that at least 50 other young men from their neighborhood had gone to join ISIS and that many others were on the way to do the same, she could not give up on her son.

Saad, who asked that her whole name not be used for security reasons, says she went to the center where all the young men were volunteering and managed to get an appointment with the emir, or leader, who was responsible for that particular group of volunteers. In tears, Saad begged him to release her son, who was her family’s only provider; Saad also has six daughters. She told him that she had lost her older son but couldn’t bear to lose her second son, too.

The emir agreed to release Saad’s son from ISIS. Locals say this is not the first time this has happened. The emir often receives household heads asking him to let their sons leave ISIS and apparently he often responds positively.

Previous to ISIS’s arrival, it seemed many young people in Mosul were opposed to them because of their cruel methods, killing and bombing. But since the group took control of the city, some of these same young people have started to become supporters and soldiers for ISIS. The great fear they have now is what might happen to them if the Iraqi government and the militias supporting it gain control of Mosul again.

Some young men in Mosul who have not enlisted also worry that ISIS may start a conscription system, once it runs out of willing volunteers. This fear was exacerbated when one of the city’s tribal leaders received a request asking him to send a certain number of men from his tribe to join ISIS.

There are still a large number of young people in Mosul who do not want to join ISIS. This is especially true of the better-educated youth. As one of them says, they have chosen to stay in their homes because, while they may have some political anti-government sympathies, they “don’t want to join hands with those whose hands are stained with blood.”

Those Mosul locals who have avoided volunteering say they think the new volunteers will soon try to leave the organization again, once the glamour wears off.

No doubt those who stay with ISIS will be the likes of Abdullah, whose childhood innocence has been stolen by group, and who will simply become one of the increasing numbers of children patrolling Mosul’s streets with guns. Unfortunately now seeing a child like Abdullah, armed and shopping for candy in a mask, is no longer a surprise; it is a sight to which Mosul’s citizens have become accustomed.

This article is adapted from a report published on the site Niqash.org.