The International Criminal Court at The Hague, Netherlands, in its first verdict, found Congolese warlord Thomas Lubanga guilty of sending children into battle. The unanimous decision found that the evidence, which included video footage and witness\' testimony, proved beyond reasonable doubt that Lubanga and others knowingly drafted children younger than 15 to fight for the military unit of his Union of Congolese Patriots during the Democratic Republic of Congo\'s civil war in 2002 and 2003, Voice of America reported. \"The chamber concludes that the prosecution has proved beyond reasonable doubt Mr. Thomas Lubanga is guilty of the crimes of conscripting and enlisting children under the age of 15 years into the [Union of Congolese Patriots] and using them to participate actively in hostilities,\" the opinion said. Lubanga was the first person tried by the permanent war crimes tribunal, established in 2002. The trial began in 2009, three years after Lubanga was arrest. Lubanga, who can appeal the verdict, will remain in custody until he is sentenced, VOA said. Observers told The New York Times the decision was important because it established the use of children in war as an international crime. Human rights groups estimate more than 250,000 children are being used as messengers, bodyguards, soldiers or sex slaves in hostilities in more than 30 countries. A monitor of the tribunal said the International Criminal Court must assess why it its first trial took a decade. \"The court needs to conduct a lessons-learned exercise to assess why the case took as long as it did,\" Sunil Pal, the Coalition for the International Criminal Court\'s top legal officer, told the Financial Times before the court delivered its verdict against Lubanga. Backed by 120 countries -- but not the United States, Russia or China, among others -- the court opened July 1, 2002, to prosecute individuals for genocide, crimes against humanity and war crimes committed on or after that opening date. It was established as a permanent institution independent of the United Nations, intended to replace ad hoc panels such as the Nuremberg military tribunals that prosecuted German Nazis after World War II, or the more-recent U.N. courts that have dealt with Rwanda and Yugoslavia. A 1998 Rome treaty establishing the court removed head-of-state immunity for atrocity crimes. Beginning in 2017 it can prosecute \"crimes of aggression,\" or military conflicts waged without the justification of self-defense.