Former Kosovo President Hashim Thaci has pleaded not guilty to 10 counts of war crimes and crimes against humanity.
He went on trial on Monday with three co-defendants, accused of killing nearly 100 people and other atrocities including enforced disappearances.
The allegations date from Kosovo's independence war against Serbia in 1998-99 in which more than 10,000 died.
Mr Thaci was co-founder of a group fighting for independence and is regarded as a hero in Kosovo.
The Kosovo Liberation Army (KLA) was set up in the early 1990s as a militant group of ethnic Albanians, in what was then a province of Serbia, and during the war is alleged to have carried out attacks on the region's ethnic Serb minority.
When Kosovo declared its independence in 2008, Mr Thaci became its first prime minister and later president, but resigned in 2020 to face the charges in The Hague.
Victims and human rights groups hope his trial - at a special court known as the Kosovo Specialist Chambers - will reveal what happened to some of the thousands of people who vanished during the Kosovo conflict.