Two retired Croatian generals have been convicted of atrocities against Serbs during the break up of Yugoslavia in the 1990s, after a trial at The Hague.
Judges sentenced Ante Gotovina to 24 years and Mladen Markac to 18 years in jail for crimes including murder, persecution and plunder.
The men helped to plan an operation to retake Croatia's Krajina region and force out all Serbs in 1995.
The Croatian government and public have reacted angrily to the verdict.
The BBC's Mark Lowen in Zagreb says crowds who had gathered to watch the tribunal's hearing on big screens in the Croatian capital booed and hissed when the judge announced the guilty verdicts.
The men are regarded as heroes by many in Croatia.
The UN war crimes tribunal cleared a third defendant, Ivan Cermak, of all charges.
Gotovina and Markac were convicted of a range of war crimes and crimes against humanity committed as their forces retook the Krajina region, which had been under Serbian control since the start of the war in 1991.
About 200,000 ethnic Serbs were driven from Croatia in 1995 and at least 150 were killed in a military offensive known as Operation Storm.
The fast-paced military operation, ordered by former Croatian President Franjo Tudjman, began with heavy shelling of the area, which forced many Serbs to flee to Serbia.
During his verdict, Presiding Judge Alphons Orie characterised the operation as a "joint criminal enterprise" between the military commanders and Mr Tudjman, who died in 1999 while under investigation by the tribunal.
Judge Orie said there had been widespread and concerted attacks on the Serb civilian population in Krajina.
"The Croatian military committed acts of murder, cruel treatment, inhumane acts, plunder, persecution and deportation," said the judge.
Both Gotovina and Markac had played a part in planning and overseeing this operation, the court ruled.
Lawyers for both of the convicted men said they would appeal against the verdicts.
Croatia's Prime Minister Jadranka Kosor said implicating the government in a criminal enterprise was unacceptable.
She said the operation was legitimate and aimed at liberating Croatian territory from occupation.
"My government will do everything possible within the legal framework to get these qualifications withdrawn," she said.
The aftermath of the war is a key issue both in Croatia's domestic politics and its external relations.
The EU has made it clear to former Yugoslav republics that they will not be considered for membership until war criminals are brought to justice.
Gotovina's arrest in 2005 was considered crucial to Croatia's chances of joining the bloc.
War veterans, many of whom turned out in Zagreb to protest at the verdicts, are a powerful lobby group in the country.
"All of us have been convicted, including the Republic of Croatia," said protester Branko Borkovic, a former army commander.