A mother-of-three who was funded by "jihadists" to take her children to Syria has had them taken into care.
The family, who cannot be identified, were stopped at Birmingham Airport moments before boarding a plane.
Her mobile phone was found with so-called Islamic State images and pictures of masked children with guns.
After Leicester City Council brought care proceedings, the High Court ordered the youngsters live with their grandparents but with supervision.
The children's father is believed to have fled Britain in 2013 and is now in Chechnya with a terrorist group, Mr Justice Keehan said.
Specialist officers from the Counter Terrorism Unit swooped on the family in July last year as they were about to leave for Munich.
The mother claimed they were heading off on holiday but a search of their nine cases revealed a travel itinerary to Turkey.
Hidden inside a pack of painkillers were telephone numbers including a suspected Islamic State militant based in Syria.
The family home appeared to have been abandoned and a search found a second mobile phone, which showed the mother had been in regular contact with a "prominent member" of IS.
The details of the case came out after Leicester City Council brought proceedings to formally place the children, who have been living with their maternal grandparents, in care.
Mr Justice Keehan concluded that the mother lied "almost throughout the entirety of her evidence" and that links to Syria and IS had been proved.
He added that money the mother was found with "had come from jihadist supporters".
"The intention to cross into Syria was driven by religious ideology and placed the children at risk of suffering significant harm and probable radicalisation.
"That included the real possibility of the children being drawn into the war and being placed at risk of death", he said.
He said that it was understandable that the children wanted to live with their mother but that it was in their best interests they live with the grandparents.
They will be supervised by the council.
Mr Justice Keehan's decision was made in January but has only just been published.