PARIS -- Bosco Ntaganda, the Congolese rebel commander with a reputation for extreme brutality, did not live up to his nickname "The Terminator'' on Tuesday when he appeared for the first time at the International Criminal Court on charges of rape, murder, sexual slavery and using children as soldiers.
Wearing a court-issued dark suit, Mr. Ntaganda seemed timid and anxious, cutting a slight figure next to one of the burly guards the court had chosen for the occasion. Although Mr. Ntaganda, long a wanted man, was not asked to enter a plea, he quickly told the judge and a room full of black-gowned lawyers, ''I was informed of these crimes, but I plead not guilty.''
When the judge, Ekaterina Trendafilova, asked him to state his profession, Mr. Ntaganda, 39, said simply, ''I was a soldier in the Congo.''
It was an understated summary of Mr. Ntaganda's career, which spanned almost 20 years of fighting, first in Rwanda, then in an array of rebel groups vying for control over a mineral-rich part of eastern Congo, and even a stint as a general in the Congolese Army. According to the prosecution, Mr. Ntaganda was one of the most ruthless and cruel of Congo's rebel leaders.
During operations he led in the early 2000s, according to the prosecution, Mr. Ntaganda's warfare of choice was not military confrontation but a sweeping campaign that involved terrorizing villagers, pillaging, raping, killing and using drugged children as his foot soldiers and henchmen.
The international court first issued an arrest warrant for him in 2006 and another in 2012, but Mr. Ntaganda lived openly, seemingly untouchable, until he unexpectedly arrived at the American Embassy in Kigali in Rwanda last week and asked surprised diplomats to turn him over to the I.C.C.
Intriguing questions about what prompted the warlord to turn himself in remained unanswered on Tuesday, as the issue was not addressed during the hourlong arraignment hearing in court.
But there was a moment of bemused surprise among observers when Mr. Ntaganda's court-appointed lawyer said that his client would ask to be released until the start of the trial. Such a request is unlikely to be granted to a man who has been on the run for years.
One theory suggests that by entering the American embassy in Rwanda, Mr. Ntaganda looked to save his life after feeling threatened by members of his own rebel group, known as M23. The group had recently split, leading him and about 700 of his men to flee across the border into Rwanda.
He was on a list of wanted men whose capture the United States government would pay a hefty reward for, exposing him to additional risk.
Some experts who focus on the region said that the Rwandan government, which had long backed Mr. Ntaganda and his rebels, had urged him to give himself up because it wanted to rid itself of an ally who had become too much of a liability. They said Mr. Ntaganda had gained a reputation not only as brutal commander, but also as a crime boss in the region around Goma, one of Congo's biggest cities, where he reportedly had been engaging in gold deals and extorting local businessmen. Rwanda plainly told him that it could no longer protect him, one expert said.
Stephen J. Rapp, the American Ambassador for war crimes, who knows the region well, said: "I don't know how or why Ntaganda came to the U.S. Embassy in Rwanda. For him, this route may have offered the least disadvantages.''
Although neither the United States nor Rwanda are members of the international court, the two agreed to cooperate to deliver the rebel leader to The Hague, where he was flown in a private plane late Friday.
The removal of Mr. Ntaganda from the conflict zone may be seen as a relief, but it is not expected to bring stability to the region.
Rwanda has been seen as an important destabilizing factor in eastern Congo, with United Nations investigators drawing up detailed reports that the Rwandan government had been covertly supporting Mr. Ntaganda's men and other rebel groups to profit from the lucrative mineral trade across the border. Several Western nations, including the United States, have cut aid to Rwanda and pressured the government to cut their ties to the Congolese rebel groups.
''We want there to be peace in the region,'' said Mr. Rapp, a former international prosecutor, who said that in his present job he had been to Congo eight times and had "seen the horrors inflicted on the people.'' At one point, in the town of Kiwanja, he said, "I met a woman who had seen the throats of her eight children slashed before her eyes, allegedly by men under Bosco's command.''
''There were local prosecutions, but Bosco and his men were above the law," he added. "When one was arrested he was broken out of jail.''
The judge, in reading the charges against him, said Mr. Ntaganda was accused of the war crime of enlisting and using children under the age of 15 as soldiers, and of crimes against humanity, including murder, rape, sexual slavery and pillaging.
Last year, the court sentenced Thomas Lubanga, a former associate of Mr. Ntaganda, to 14 years in prison for enlisting child soldiers. The prosecution charges that Mr. Ntaganda was the main person in charge of conscription.
During much of the hearing, Mr. Ntaganda was clearly uncomfortable in the sleek modern courtroom, often looking down or hunching over as if wanting to disappear. He told the court he was born in Rwanda but had grown up in Congo and was a Congolese citizen. When the judge asked if he spoke English or French, the languages of the court, Mr. Ntaganda said, ''I understand French somewhat, but I speak Kinyarwanda,'' the language of Rwanda.
The next hearing in the case was set for April 15.
This article originally appeared in The New York Times.