The Islamic State of Iraq and al-Sham, or ISIS, allowed a VICE News crew to interview them, and document their activities, in a five-part series on the caliphate.

The extremist Sunni Muslims have persecuted and killed thousands of Christians and Shiite Muslims across Iraq and Syria, and driven hundreds of thousands of civilians from their homes. The most recent VICE video, published last week, shows young children apparently admiring the terrorists, The Blaze reports.

One man, known as Abdullah Al-Belgian, left Belgium with his son to fight alongside ISIS. He quizzed his son on camera about the terrorist regime.

"What is over there [in Belgium]?" he asked.

"Infidels," the boy answered.

"What do you want to be, a jihadist or to execute a martyrdom operation?"

"A jihadist," his son said.

"What have the infidels done?"

"They kill Muslims."

Another militant expressed satisfaction that a generation of children are growing up under a strengthening caliphate. Led by Abu Bakr al Baghdadi, ISIS has increased in power substantially since the withdrawal of U.S. troops from Iraq in December 2011.

"For us, we believe that this generation of children is the generation of the caliphate," the fighter told VICE reporters.

"God willing, this generation will fight infidels and apostates, the Americans and their allies, God willing. The right doctrine has been implanted in these children. All of them love to fight for the sake of building the Islamic State and for the sake of God."

Children as young as nine years old appear on the video, declaring their allegiance to the Islamic State. One boy said that after Ramadan, he will go to ISIS training and learn how to use a Kalashnikov rifle.

"What are you going to do after?" the interviewer asked.

"To fight the Russians... America. The infidels," he answered.

"Those under 15 go to Sharia camp to learn about their creed and religion," Islamic State Press Officer Abu Mosa explained.

"Those over 16, they can attend the military camp."

The United Nations reported last month that over 5,500 Iraqi civilians were killed by ISIS in the first six months of the year.