A top Lord's Resistance Army commander is now in custody at the International Criminal Court in The Hague.
Dominic Ongwen will undergo medical exams after being flown Tuesday from the Central African Republic, and is expected to make his first court appearance soon.
His arrival at the court ends a nearly 10-year effort to have him face three counts of crimes against humanity and another four counts of war crimes.
ICC prosecutor Fatou Bensouda said Wednesday that Ongwen was "among those who bear the greatest responsibility" for LRA atrocities. The group is accused of killing and kidnapping tens of thousands of people across Uganda and three nearby countries over the past 30 years.
United Nations Secretary-General Ban Ki-moon said Ongwen's arrival in The Hague "marked an important milestone in accountability" and a step toward justice for those victimized by the LRA.
Bensouda said Ongwen's transfer to the court sent a "firm and unequivocal message" that perpetrators of the most serious crimes would face justice no matter how long it takes.
The court has charged four other ICC leaders with war crimes and crimes against humanity, including LRA chief Joseph Kony.
An African Union task force is searching across central Africa for Kony and the few remaining bands of LRA fighters. Ongwen surrendered in the Central African Republic earlier this month.