Thomas Lubanga was convicted in March of recruiting and using children in his Union of Congolese Patriots militia, sending them to kill and be killed during fighting in Congo’s eastern Ituri region in 2002-2003.
“The vulnerability of children means they need to be afforded particular protection,” he said at the sentencing hearing.
The 51-year-old Lubanga is the first person convicted by the 10-year-old permanent war crimes tribunal.
Rights activists hailed the case as a milestone in efforts to prosecute the widespread use of child soldiers in conflicts around the world.
Prosecutors had asked for a 30-year sentence, but said they would be willing to cut it to 20 years if Lubanga offered a “genuine apology” to victims of his crimes.
Lubanga, wearing a gray suit and tie, showed no emotion as Fulford read out the sentence. He can appeal his conviction and sentence.
Fulford said that time Lubanga has served in pretrial detention since March 2006 would be deducted from the sentence.
It was not immediately clear where Lubanga would serve his sentence. The court has no prison cells for holding convicted war criminals.
Fulford gave Lubanga three sentences of 13, 12 and 14 years for conscripting, enlisting and using child soldiers but the sentences are to be served concurrently.
Conscripting involves abducting children and pressing them into military service while enlisting them can be done voluntarily.