The man once dubbed "The Terminator" told the International Criminal Court about his time as a young soldier.
Almost two years after his trial opened, Bosco Ntaganda took the stand for the first time expected to talk about events in 2002 and 2003, when his rebel forces rampaged through neighbouring Democratic Republic of Congo's gold-rich Ituri province, murdering and raping civilians and plundering their possessions.
Instead, the man once dubbed "The Terminator" told the International Criminal Court about his time as a young soldier in the Ugandan-backed Rwandan army during that country's genocide in which some 800,000 people, mainly Tutsis, were murdered.
"I was young, but I was already in the army and was a soldier," said Rwandan-born Ntaganda, who is now accused of playing a major role in the unrest in the eastern DRC in 2002-03.
"I witnessed horrific events," he told the Hague-based ICC, adding "I lost many members of my family during the genocide against the Tutsis."
"Our superiors had told us what we have just seen as soldiers -- if possible we had to do everything to prevent this from happening in Africa again," the soft-spoken Ntaganda said, speaking in Swahili.
"This was in my mind wherever I went. I do not wish to see any other community experience what my community went through," said Ntaganda, who was smartly dressed in a dark blue suit, light shirt and blue tie.
Ntaganda, 43, denies 13 charges of war crimes and five counts of crimes against humanity committed by his Patriotic Forces for the Liberation of Congo (FPLC), a militia drawn from the Hema ethnic group which prosecutors say targeted the Lendu and other non-Hema groups.
Fighting in Ituri has left some 60,000 dead since 1999 according to rights groups, in a conflict exacerbated by the wealth of regional resources including gold and other minerals used in electronic products.
Ntaganda has been charged with ordering hundreds of deaths through savage ethnic attacks by the FPLC, which was then the armed wing of the Union of Congolese Patriots.
During the prosecution's case, which took 64 days to complete, a witness told the tribunal in The Hague of seeing "tied-up bodies" left in their underwear, "their heads crushed."
Ntaganda "was one of the most important commanders" involved in the savage ethnic attacks carried out by the FPLC, ICC chief prosecutor Fatou Bensouda said at the opening of the trial in September 2015.
The eastern Democratic Republic of Congo has been mired for two decades in ethnically-charged wars, as rebels battle for control of mineral resources.
The unrest spiralled to encompass armies from at least six African nations, claiming hundreds-of-thousands of lives in one of the world's most deadly recent conflicts.
At the start of his trial Ntaganda, known for his trademark pencil moustache and his penchant for cowboy hats and fine dining, told the judges he rejected being called "The Terminator".
The ICC issued two arrest warrants against Ntaganda who evaded capture until unexpectedly walking into the US embassy in Kigali in 2013 and turning himself in.
Ntaganda's defence team plans to call 109 witnesses and four experts, seeking to overturn his image as a merciless warlord.
The former rebel went on a two-week hunger strike last year after judges slapped tight restrictions on him when prosecutors accused him of bribing witnesses.
If convicted he could face up to 30 years behind bars, or life if such a sentence is "justified by the extreme gravity of the crime," under ICC rules.
Ntaganda's case follows that of his former boss, warlord Thomas Lubanga, who was sentenced to 14 years in jail in 2012 on similar charges, the court's first conviction since it opened in 2002.