Over 31,000 pregnant women are living or trapped inside ISIS [Daesh] territory where children are indoctrinated into becoming jihadi child soldiers in Syria and Iraq.
The shocking findings have been uncovered by experts from the Quilliam foundation, a counter-extremism think tank based in London.
It is thought that 50 British children are among the child soldiers learning to become fighters for the jihadi group in Syria and Iraq.
ISIS have been accused of copying the Nazis' recruitment tactics to brainwash young boys into becoming its next generation of killers.
Child soldiers frequently appear in their propaganda photos and videos, with children from different nations being videoed executing prisoners and delivering hate-filled messages to their homelands.
One video even showed a French child soldier beheading a man with a sharp knife, while a more recent video showed how ISIS made several 'cubs' hunt and kill spies in an old castle.
The United Nations has recently received reports the group has begun an official youth wing, Fityan al Islam - or 'boys of Islam'.
By studying ISIS propaganda and speaking to sources living among ISIS, Quilliam said the group is desperate to recruit young and impressionable children to 'safeguard its future'.
It said many of them are being turned into spies, soldiers, suicide bombers and executioners.
Children are shown being forced to learn and recite the Koran as well as undergo fitness and weapons training in the countryside.
The report stated: 'The organisation [ISIS]... focuses a large number of its efforts in indoctrinating children through an extremism-based education curriculum.
'The current generation of fighters sees these children as better and more lethal fighters than themselves.
'Rather than being converted into radical ideologies they have been indoctrinated into these extreme values from birth, or a very young age.'
The report said these boys 'are better and more brutal fighters as they are trained in violence from a very young age'.
It also compared ISIS's focus on youth to the child soldiers forced to fight for Liberian dictator Charles Taylor's rebel army in the 1990s - and the Nazi regime which created the Hitler Youth to brainwash children.
The report found that children were used heavily in ISIS propaganda between August and February, with more than 250 propaganda releases featuring children.
The terror group is also said to 'normalise' them to brutality from a young age by forcing them to hold the heads of decapitated victims - or play football with them.
In the last six months, it has released videos of at least 12 children killing victims, including a four-year-old British boy who blew up a car full of trapped hostages.
The UN Mission in Iraq said ISIS has abducted up to 900 children aged nine to 15, and many of them are forced to go to ISIS controlled schools.
Here, they are immersed in ISIS's twisted curriculum, desensitised to violence and taught the skills needed to wage a holy war on the West.
Quilliam also found that ISIS uses fear to recruit young boys by threatening those who defy them with floggings, torture and rape.
The Roméo Dallaire Child Soldiers Initiative, which co-wrote the report, said life under ISIS is 'one of the gravest situations for children on Earth'.
Its spokesperson told the Guardian: 'It is hoped that this report will provide a critical perspective on the plight of these children, that will then create essential reflections for policymakers, child protection agencies, governments, multilateral organisations, and those concerned with ending conflict in Iraq and Syria.'
By Tom Wyke
© Associated Newspapers Ltd.