They are "graduates" of a group called Saddam's Lion Cubs, often kids from dissident parents who have been turned even against their parents through the Iraqi state's education system from an early age. Parents have virtually no choice in the matter if their children are selected. It's like a sick version of the boy scouts. Kids are trained from an early age to kill animals to harden them for brutalizing people later on. This training is given to both girls and boys. It may be that Saddam uses children of imprisoned or dead dissidents as trainees and others as available.
Maybe we should ask Scott Ritter about that children's prison he saw a while back.
I would say the closest thing we have to them are inner city gang members. But theirs are trained.
For some reason dictatorial thugs have a real thing for using children in war. They know we aren't the type to be all that well prepared psychologically to fight such young people.
See this :
And a VERY interesting PDF file :
Saddam has since the 1970s advocated taking kids away from parental influence at an early age in order to train loyalists.
Kind of like public schools in the U.S.
Even have their own website "Baathist Underground".