ISTANBUL — They call them the “cubs of the caliphate” and one of them, a French national who looked like a 12-year-old, was filmed last week shooting an accused spy in the forehead, then pumping additional rounds into his body.

In the execution video posted by the extremists a new militant song can be heard playing in the background: “We have come, we have come, we have come, as soldiers for God. We have marched, we have marched, we have marched, out of love for God. We know religion, we live by it; we build an edifice, we ascend it. We deny humiliation we have experienced; we put an end to idolatrous tyranny.”

He is not the first child soldier to be showcased by the jihadists carrying out executions in scenes that invoke the bestial madness of Cambodia’s Khmer Rouge in the 1970s. And likely he won’t be the last as the so-called Islamic State, widely known as ISIS, becomes ever more systematic recruiting and brainwashing any children it can get hold of, whether they’re the children foreign fighters brought along with them or local kids from Iraq and Syria.

Much of the media attention on the use of child soldiers is focused on the children of the foreign fighters, hardly surprisingly as they are the ones featured in the execution videos. (The 12-year-old murderer is believed to be French.) They also appear in the social media feeds of foreign fighters: In August an Australian jihadi in Raqqa, the de facto capital of ISIS in northern Syria, posted a photo on Twitter of his 7-year-old son holding up a severed head with the caption “That’s my boy.” The abducted children of slaughtered Yazidis and other ISIS opponents have been added to the juvenile ranks as well.

But the greater effort by ISIS is focused on the much larger numbers of local kids—a cadre-in-waiting, as far as the militants see them—who can be transformed into warriors and suicide bombers or spies to help ISIS search out dissent and warn of resistance to its rule among the local population.

Many of the reinforcements ISIS sent to Kobani, the mainly Kurdish Syrian border town that defeated a months-long siege by the militants in January, reportedly were Syrian and Iraqi youngsters.

The militants are ramping up efforts to indoctrinate children in territory they control across Syria, issuing registration papers this month to local parents and now requiring them to send their kids to schools controlled by the terror army. Teachers, if they want to continue to work, have to swear allegiance to the terror group and teach the curriculum supplied by the militants. And the teachers are being ordered to inform on any children not attending schools.

The push to control the children of the caliphate and to turn them into murderous cubs is partly a consequence, Syrian rebel commanders think, of the high death toll the militants have suffered as a result of U.S.-led coalition airstrikes, the prolonged struggle for Kobani and battles in Iraq and northeast Syria with the Kurds. This month Gen. Lloyd Austin, who heads up U.S. Central Command, told the House Armed Services Committee that the bombing campaign against ISIS had likely killed upwards of 8,500 fighters.

Some analysts question that estimate, arguing the U.S. has no comprehensive on-the-ground damage assessment capability to help calculate the casualties inflicted by airstrikes. Even so, its clear the militants are suffering significant casualties. Rami Abdurrahman, who heads the London-based Syrian Observatory for Human Rights, a pro-opposition monitoring network of political activists in Syria, estimates that ISIS lost more than a thousand fighters at Kobani. He sees that death toll as a crucial reason behind the group’s failure to overrun the town.

A U.N. report on war crimes in Syria warned that ISIS indoctrination of children is creating a “cadre of fighters that will see violence as a way of life.”

But the need for more front-line fighters isn’t the only prompt for the increasingly systematic harnessing of the children of the caliphate. As with the repressive and genocidal Khmer Rouge, who indoctrinated thousands of children to help usher in “Year Zero,” and before them the Bolshevik revolutionaries of Russia, ISIS militants see education as crucial in their determination to create the new society.

The methods employed echo those adopted by the secular totalitarian Soviets and their satellites. As one Soviet schooling theorist argued in 1918, “We must make the young into a generation of Communists. Children, like soft wax, are very malleable and they should be molded into good Communists.”

The ISIS militants are setting out to do the same, but instead of producing Communists they want to manufacture good jihadists. Unlike the Soviets, who set out to nationalize children and to “rescue them from the harmful influence of the family,” Islamic militants don’t talk in terms of children being the property of the Islamic State, but that is what they are fast becoming as the jihadists monopolize control of daily life, monitor families as they do so.

Elementary and middle schools in Raqqa only reopened last month — high schools remain closed — and according to local activists with the network “Raqqa is Being Slaughtered Silently” parents are so fearful of their children being brainwashed many are keeping them home. Registration papers for ISIS schools are being sent to parents along with an undertaking they are meant to sign that states: “I pledge, by God willing, to send my son to the school in order to continue his studying, in the case of not carrying this out I will take full responsibility.”

According to the Syrian Observatory, teachers at the schools have been ordered to warn parents of students who don’t attend that they must send them. Last month, the ISIS distributed job applications for teachers and in the province of Deir Ezzor the applicants had to repent for teaching in Syrian government schools previously and sign a declaration stating, “I, the undersigned, repent to Allah for teaching blasphemous, nationalistic and atheistic curriculums, working under man-made laws.”

“Those who will not pledge allegiance aren’t allowed to teach,” says the Syrian Observatory. The approved ISIS curriculum contains six main subjects: monotheism, Arabic Language, mathematics, physics and chemistry, biology, and English Language. A key texts used in lessons for monotheism are Wahhabi ones.

Indoctrination efforts of the young are widespread. The high schools remain closed to encourage older children to attend the group’s military youth camps. The offer of payments prompts some impoverished families to send their children to the camps established by the militants—in much the same way they find it hard to forgo the offer of payments when it comes to their kids joining up as fighters. When payments don’t work, the militants have resorted to kidnapping children and taking them to youth camps without permission of their families.

And the campaign of indoctrination is present outside the camps, too: in the local mosques, all of which are fully under the militants’ control; at outdoor events the group organizes, where videos of executions and battles are screened. “There are many kids who are indoctrinated through the Da’wah (proselytizing) tents,” says anti-ISIS activist Abu Ibrahim Ar-Raqqawi.

And the nonstop, every-where-you-look campaign is having an impact, as activists tell of children playing at being Islamic militants. Peer pressure makes them want to identify with ISIS. One child interviewed by Human Rights Watch for a report last year on recruitment by armed groups in Syria said: “When ISIS came to my town ... I liked what they are wearing, they were like one herd. They had a lot of weapons. So I spoke to them, and decided to go to the training camp in Kafr Hamra in Aleppo.”

“While children have often been victims of such manipulation in war zones, ISIS approached their ‘education’ as it did almost everything else—systematically,” note analysts Jessica Stern and JM Berger in a new book, ISIS: The State of Terror. They add: “ISIS actively recruits children to send them to training camps and then to use them in combat and suicide missions. It has used children as human shields, suicide bombers, snipers and blood donors.”

In al Bab, a town northeast of Aleppo, teenagers are wary of venturing outside too much, fearful of being questioned about why they have not joined up as fighters. “I was interrogated for a long time at a checkpoint when I was visiting my family in al Bab about why I hadn’t volunteered to fight,” says Mohammed, who is studying in Turkey.

The militant targeting of youngsters also affects the private lives of families. Children have been heard accusing their parents of being apostates for not allowing them to join the militants or openly criticizing them for failing to keep strictly to the militants’ interpretation of Sharia law. ISIS has published a guidebook instructing mothers on how to raise their children to ensure they become the kind of Muslims the jihadists demand. They should tell them bedtime stories about jihad and martyrdom and direct them away from television and encourage them to watch the videos of ISIS exploits.

“Parents are now being careful what they say in front of their children—some worry their own kids will report them,” says father-of-two Sami, a Raqqa man, who recently fled to Turkey. “People are talking in whispers.”