Relatives of victims are heading to The Hague for the trial
The indictment against him is breathtaking in its scale.
Radovan Karadzic stands accused of leading a huge criminal enterprise, involving genocide, extermination and the forced expulsion of non-Serbs from their homes.
The document runs to more than 60 pages and cites hundreds of individual crimes.
In Sarajevo, for example, in November 1994, a young mother called Dzenana Sokolovic was struck in the abdomen by a sniper's bullet while she was out collecting wood.
The bullet passed straight through her and struck her seven-year-old son Nermin in the head, killing him instantly.
Mrs Sokolovic survived and is ready to come to The Hague to testify against Radovan Karadzic.
"I would," she told me last week, "go to the moon to get justice for my son."
This lingering sense of justice not yet done is the unfinished business of Bosnia's three-and-a-half-year war.
The document charging Radovan Karadzic cites hundreds of crimes
Among the charges Mr Karadzic faces is responsibility for the siege of Sarajevo.
Bosnian Serb forces surrounded the city on all sides and throughout the war subjected it to shelling and sniping.
The intention, the prosecution claims, was to terrorise the civilian population.
The worst single atrocity of the war occurred at Srebrenica in eastern Bosnia.
When it fell to Bosnian Serb forces more than 7,000 Muslim men and boys were rounded up and murdered in the space of a few days.
The prosecution say Radovan Karadzic carries his share of responsibility for this too.
Mr Karadzic was the leader of the Bosnian Serbs.
In 1992, when Bosnia declared independence from the disintegrating Federal Republic of Yugoslavia, Mr Karadzic formed a separate state, later to be called Republika Srpska.
Bosnian Muslim victims were found in mass graves
The aim was to create an independent homeland for the Serbs of Bosnia.
Hundreds of thousands of non-Serbs were driven from their homes in a campaign that came to be known as "ethnic cleansing".
Radovan Karadzic denies all the charges.
Few dispute that the crimes outlined in the indictment took place.
Many others have already been convicted of them and are serving prison sentences.
But the prosecution will have to establish a direct line of culpability between the men who wielded the weapons and pulled the triggers, and Radovan Karadzic in person, sitting at his desk at his mountain headquarters in Pale.
The court has given the prosecution hundreds of hours of witness time to try to do just that.
Mr Karadzic has the right to cross examine the prosecution witnesses and to call witnesses of his own.
He intends to represent himself. He has decided to co-operate with the court to prove his innocence.
The trial could last many months, even years.