Prosecutors at The Hague have accused former Bosnian Serb army commander, Ratko Mladic, of being behind a carefully planned, state-sponsored conflict in the 1990s in which many people were casually murdered.
On the first day of General Mladic's trial on war crimes charges, the prosecutor, Dermot Groome, said Mladic had set himself the goal of ethnically cleansing much of the territory.
Mr Groome told the court about what happened to a group of non-Serb men in northern Bosnia, the BBC reports.
"They were loaded - in groups of five - into a bus. The bus was driven to a field, and as the men were forced off the bus, they could see the bodies of those killed before them. They were murdered as they left the bus," he said.
General Mladic faces 11 counts of war crimes and crimes against humanity, including genocide, in connection with the brutal 1992-95 Bosnian war.
Charges include the massacre of more than 7000 Bosnian Muslim men and boys at Srebrenica in 1995. He is also charged in connection with the 44-month siege of Sarajevo during which more than 10,000 people died.
He has called the accusations "monstrous" and the court has entered a "not guilty" plea on his behalf.
Prosecutors in The Hague said he intended to "ethnically cleanse" Bosnia, and they would show his hand in the crimes.
General Mladic, dressed in a dark grey suit, applauded and gave a thumbs-up as the judges walked in, and the BBC reported the 70-year-old might have been physically diminished from the swaggering war leader of 20 years ago but was proud and defiant as ever.
War described by the prosecution was not one of ancient ethnic hatreds, but a carefully planned criminal enterprise that was well orchestrated, centrally directed and state-sponsored.
General Mladic's voice, from a recording in 1993, boasted that "every time I go by Sarajevo, I kill someone in passing. I kick the hell out of the Turks (offensive term for Bosnian Muslims)".
It was a reminder of the terror that once prevailed in Bosnia, and of the violent abandon with which the aim of building an ethnically pure Serb state was pursued.
The prosecution opened the hearing at the International Criminal Tribunal for the former Yugoslavia (ICTY) with an audio-visual presentation laying out the case against General Mladic.
"Four days ago marked two decades since Ratko Mladic became the commander of the main staff of the army of Republika Srpska - the VRS," said Mr Groome.
"On that day, Mladic began his full participation in a criminal endeavour that was already in progress. On that day, he assumed the mantle of realising through military might the criminal goals of ethnically cleansing much of Bosnia. On that day, he commenced his direct involvement in serious international crimes."
Mr Groome said that by the time General Mladic and his troops had "murdered thousands in Srebrenica", they were "well-rehearsed in the craft of murder".
He then showed judges video of the aftermath of a notorious shelling of a market in the Bosnian capital Sarajevo, in which dozens of people died.
Mr Groome said there was "no doubt" that General Mladic had controlled the shelling of Sarajevo. He had promised that the city would shake, the prosecutor said.
Mr Groome said the attacks were part of an "overarching" plan to ethnically cleanse non-Serbs from parts of Bosnia.
General Mladic has been awaiting trial in the same prison as his former political leader Radovan Karadzic, who was arrested in 2008 and is now about half-way through his trial on similar charges to General Mladic.
Mr Groome said crimes of sexual violence had played an integral part of the process of "taking over and ethnically cleansing Bosnia".
"While women were most often targeted for such crimes of terrible violation, men were also victims," he said.
In the third and final session of the day, the prosecution highlighted the role of snipers in Sarajevo, showing images of a child shot dead on a street and pictures taken from sniper nests overlooking the besieged city.
Hearings in the trial were later adjourned until Thursday (Friday, NZ time).
While General Mladic's critics consider him a butcher, to some Serbs he is a national hero.
General Mladic suffered at least one stroke while in hiding and remains in frail health.
Key architect of the Balkan wars, former Serbian President Slobodan Milosevic, died in detention in his cell in 2006, before receiving a verdict.