The trial of former Ivory Coast President Laurent Gbagbo for crimes against humanity is set to begin at the International Criminal Court (ICC).
He faces charges relating to the country's civil conflict that erupted after he lost elections in 2010.
The trial aims to "uncover the truth", ICC Chief Prosecutor Fatou Bensouda told reporters at The Hague.
Both Mr Gbagbo and his co-accused, former militia leader Charles Ble Goude, say they are innocent.
"The trial is an opportunity for reconciliation," Mr Gbagbo's lawyer Emmanuel Altit said. "It is for this reason that he awaits it with confidence."
A lawyer for Mr Ble Goude, who is accused of organising attacks on opposition supporters, described his client as a "man of peace".
A key test, by Anna Holligan, BBC News, the Hague
This may prove to be the most important trial in the ICC's history. The international court was established to end impunity and bring the most powerful leaders to justice. The first appearance of a former head of state is testament to the prosecutor's reach. And yet, despite casualties on both sides, not one of President Alassane Ouattara's supporters has been charged, leading to accusations of victor's justice.
During the pre-trial press briefing the victims' representative was asked how she could represent the victims when only half of those who suffered would have their voices heard.
This high-profile trial will test the ability of the ICC to obtain reliable evidence from a country in which the government has a political interest in securing a guilty verdict.
Can the suspects expect a fair trial if much of the evidence comes from their enemy?
Mr Gbagbo sparked a crisis in Ivory Coast after he refused to step down following his loss to Alassane Ouattara in the 2010 presidential vote.
Some 3,000 people were killed in the civil conflict that ensued, with Mr Gbagbo holing up in the presidential palace.
He was arrested in April 2011, by forces loyal to President Ouattara backed by French troops, and later in that year extradited to The Hague.
It will be the highest-profile trial yet for the ICC, which has only convicted two Congolese warlords since its establishment in 2002.
Mr Gbagbo is accused of four charges - murder, rape, attempted murder and persecution.
His supporters accuse the ICC of overlooking alleged crimes by Mr Gbagbo's opponents, many of whom are now in power.
But this was rejected by Ms Bensouda, who said investigations into the pro-Ouattara camp had been "intensified".

Source: BBC News