Kenya's deputy president played an important role in the post-election bloodbath that engulfed Kenya in early 2008, the International Criminal Court's prosecutor told judges at the opening of his trial today.
The most senior serving politician to appear in the dock at the Hague court, William Ruto pleaded not guilty to crimes against humanity.
Mr Ruto and co-defendant Joshua arap Sang are accused of working with other conspirators to murder, deport and persecute supporters of rival parties in the Rift Valley region.
"He assigned responsibilities, raised finance, procured weapons," over the 18 months leading up to the elections, prosecutor Fatou Bensouda told the court.
"When the election was lost, he gave the order to attack.
"The crimes of which Mr Ruto and Mr Sang are charged were not just random and spontaneous acts of brutality," she said.
"This was a carefully planned and executed plan ... Ruto's ultimate goal was to seize political power for himself and his party in the event he could not do so via the ballot box."
Prosecutors said their first witness, who had been due to speak this week, would not appear until next Tuesday.
Some witnesses have pulled out in the run-up to the trial, a setback prosecutors said was due to intimidation.
Mr Ruto's spokesman said the deputy president would return to Kenya tomorrow, after the prosecutor said witnesses had yet to arrive in the Netherlands.
He would then go back to the Hague next Tuesday when the first witness is expected to testify.
Mr Ruto's lawyer accused prosecutors of using tainted evidence and false testimony, and called on them to drop the charges.
President Uhuru Kenyatta, Mr Ruto's former rival and now his political ally, will be tried on similar charges in November.
Rival members of Mr Kenyatta's Kikuyu and Mr Ruto's Kalenjin tribes, wielding machetes, knives, and bows and arrows, went on the rampage after the disputed election, butchering more than 1,200 people and driving hundreds of thousands from their homes.
Last year, Mr Kenyatta and Mr Ruto resolved their disputes, joining forces to win a March election in an alliance they say makes violence unlikely.
Their supporters say the court cases risk undoing years of painstaking reconciliation.
Mr Ruto's lawyer, Karim Khan, listed what he said were shortcomings in the prosecution's case.
Contrary to the claim that Mr Ruto, a Kalenjin, hated the Kikuyu tribe, his sisters had both married Kikuyus, Mr Khan said.
And, he asked, how likely was it that Mr Ruto had amassed guns and grenades under the eyes of the local Kikuyu police chief?
Mr Khan played a video in which Mr Ruto called for "peaceful" action after the 2007 elections and another in which he pledged to cooperate with the court despite describing the charges he faced as "something only possible in a movie".
The case is a major test for prosecutors at the decade-old ICC, who have had a low success rate and face accusations of focusing too much on Africa.
It may also complicate relations between Kenya and the west, which sees Nairobi as central to the fight against Islamist militancy in East Africa.