While an estimated 200-300 were killed in firefights in Puntland and its neighboring region of Galmudug, Puntland's President Abdiweli Gaas tells CNN that up to 100 of them surrendered and dropped their weapons when they realized they were overpowered.
The mid-March attack was highly unusual, coming from the sea and outside Al-Shabaab's typical areas of operation.
But most unusual of all was the size of these recruits.
These were not the heroic, terrifying jihadist killers Al-Shabaab has depicted in its various propaganda videos and pictures.
These were children. Many of the fighters did not look as though they'd seen their 13th birthdays.
Not their first fight
Many of the children have battle wounds from previous fights that have yet to heal, interrogators told a CNN security source.
The young fighters have admitted to being part of previous Al-Shabaab attacks, such as a recent deadly attack on a Kenyan African Union base in southern Somalia. Some of the boys say many more like them are in the Al-Shabaab ranks.
Most of the young fighters are also dressed in combat fatigues, some with small-sized T-shirts underneath. Investigators believe, CNN is told, that these combat fatigues were stolen, along with weapons, artillery and ammunition from African Union troops.
In the pictures the boys are shown drinking milk provided by the Puntland Security Services. One Western diplomat told CNN from Mogadishu that the concern is not only what to do with these boys, it is also how many of the young ones died in the days-long fighting. Gaas says they killed "a large number of fighters" but did not specify their age.
"My interviewers from the security services told me that a lot of these kids were abducted. They didn't join Al-Shabaab voluntarily. They were taken on their way to school or they were indoctrinated and forced to fight. It's unacceptable. Kids should be in school, playing and being children. Not fighting and dying. They are losing their innocence and this is not acceptable," Gaas said.
"This is not a Somali problem, this is not a regional problem, this is a worldwide problem. This is an enemy who is fighting an ideological war -- there are boys here of 10, 12 and 15 years of age who have been brainwashed. We know we cannot just defeat Al-Shabaab militarily but also idealogically," Gaas said.
The exact numbers of the boys captured is not yet known. A source in Puntlands security services told CNN that there are 60 child soldiers currently being held in a prison in Garowe, the regional capital.
The U.N. initially said at least 16 were child soldiers, but has since revised that figure to simply state that there were "dozens." Sources CNN has spoken to estimate the number is much higher.
U.N. chief 'appalled'
The U.N. Somalia mission chief, Michael Keating, has condemned the use of child soldiers. "I am both distressed and truly appalled that anyone is using kids reportedly as young as 14 and sending them off to fight as fodder," he says. While this isn't the first time
Al-Shabaab has used children in battle, what's surprising is the number of children who surrendered.
"The sheer number of them who were sent up to Puntland, that's what is particularly shocking about it. It's one thing to have a few kids in the mix, its another to have dozens of them being sent up in units," Keating said.
The captured boys have been sent to the region's capital, Garowe, where Gaas promises they will eventually be rehabilitated. Keating said he urged fair treatment and for the governments of Puntland and Galmudug to respect international law. "It's very important that they will be well treated. This will be more productive in terms of ensuring that these children don't go back, and also understanding why they joined in the first place, which could be useful as part of broader efforts to fight the phenomenon of kids being sucked into these situations."
Gaas promises that once the young prisoners have been questioned they will be rehabilitated.
Why do terror groups use child soldiers?
For many children and their families it's simply a case of alternatives and opportunities.
"For many of the youth in Somalia there are few alternatives and so recruitment into a group that offers, money, livelihood, security, protection and status (being a "big man") might seem like an attractive option," said Mia Bloom, an academic and author whose research specializes in child soldiers.
"In many cases Al-Shabaab will recruit all the able-bodied males of a village, as well as using women. The al Qaeda groups tended to train and recruit youth and so anyone over 15 would have been free rein since in many cultures, this notion of 18 as adult is purely a westernized fiction," she says.
Using children in war is particularly useful, according to Bloom, because they have little to no sense of their own mortality.
"Often they are easily manipulated or perhaps 'modeled' by the group. They tend not to arouse suspicion and are especially useful in targeting other civilians -- with whom they might blend in," she said, adding that children are useful to terrorist groups because of "the element of surprise."
"Although the data is divided over whether they are as capable as soldiers. The children will be dedicated but may not have the patience and skills required to be top notch soldiers. If militant groups or armies just need manpower and bodies to throw at the problem this is completely different from having skilled and trained manpower," Bloom said.
Motivation for this attack
The reason behind the maneuver by the terror group, up North and away from their usual area of operations or the use of many young soldiers, is not yet fully known to security experts. Some guess one reason could be the upcoming AU planned offensive on the group, or to retreat away from air strikes and other operations launched by the United States -- one of which killed, according to the Pentagon, more than 150 Al-Shabaab fighters.
Another theory is that the Al-Shabaab fighters could have been moving on the region to attack their members who in October defected to pledge allegiance to terror group ISIS. Al-Shabaab had hunted down and killed a number of fighters who defected in the ensuing months, but one slightly larger contingent under religious leader Abdul Qadir Mumin has remained defiant, and protected by bodyguards.
Bloom says the use of so many children may indicate the group has lost older soldiers. "It's hard to know for sure, but it can be a signal that they are losing adults or having a hard time recruiting adults and thus are option for very young recruits. It could also mean that they are preparing the next generation to make sure that even if they are targeted (e.g. by U.S. drones) there is a generation ready to step into the adults' shoes," Bloom said.
On the night of March 14, the Al-Shabaab attackers on the sea, using the stolen fishing boats, split up and launched separate amphibious, or water-borne assaults from the coast on two fronts. But they were met with fierce resistance. Gaas says his security forces, their skills honed from years of fighting the terror group in the Galgala mountains, had counted somewhere in the region of 600 attackers but managed to repel them.
Experts say that Al-Shabaab's use of the sea is cause for concern. "This demonstrates that AS is prepared to use (this method) to leapfrog around the AU Mission to Somalia and Somali Federal Government forces," says John Steed, of Oceans Beyond Piracy. "It puts areas not previously threatened by Al-Shabaab at risk."