Dusan Tadic, a Bosnian Serb reserve policeman, was found guilty on 11 out of 31 counts by the International War Crimes Tribunal in The Hague yesterday.
He was cleared on nine formal counts of murder, but nevertheless found guilty of killing two Bosnian Muslim policemen on counts of "persecution", and of taking part in the murder of more than 30 people - which Judge Louise Arbour, the Chief Prosecutor, said was worse, as it was, in effect, "murder with a discriminating intent".
Tadic, 41, had pleaded innocent to all the charges. He heard the verdict of the International Court behind bullet- proof glass in Trial Chamber II.
It is the first conviction for war crimes by a multi-national court since the Nuremberg and Tokyo trials sent 17 Axis leaders to the gallows half a century ago, and the first by a tribunal which was both international and impartial.
The earlier war crimes trials were carried out by the victors in the Second World War. It was also the first formal condemnation of "ethnic cleansing" by a judicial body.
The International Court has no power to impose the death penalty and Tadic was cleared of all nine counts of murder. The three judges found him guilty on 11 counts of persecution and beatings in prison camps near Prijedor, in north-west Bosnia. Eleven counts - grave breaches of the Geneva Convention - were judged inapplicable.
Under the "persecution" counts, the court found that on 26 May 1992, Tadic had pulled two Muslim policemen from a line of prisoners in front of the Serbian orthodox church in Kozarac and killed them by slitting their throats and stabbing them several times.
He was cleared of a cruel and inhumane sexual act - forcing a Muslim prisoner to chew off another prisoner's testicle. Tadic will be sentenced at a further hearing on 1 July, giving Defence lawyers 30 days to appeal.
Legal experts said getting Tadic to trial at all was the main achievement. The alleged crimes took place during a chaotic civil war and the prosecution could not prove that the accused was linked to any of the murders, or, indeed, that individual murders had taken place.
But there will be disappointment that of 74 people indicted for war crimes, only eight, including Tadic, have so far been detained.
Martin Bell, the new Independent MP for Tatton and a former BBC war correspondent, condemned the "failure" of the international community to bring war criminals to justice.
"I think it reminds us of the relative failure of the system so far," he told BBC Radio 4's The World At One programme. "Seven of the charged are in custody, only one a major figure, and he gave himself up. The rest of the 74 are still at large - I think the figures speak for themselves."
The others include the leaders of the Bosnian Serb war effort, Radovan Karadzic and Ratko Mladic, who are still in Serb controlled territory.
The US-based group Human Right Watch said in a statement: "The international effort to achieve justice will ultimately depend not on the trial of subordinate actors like Dusan Tadic, but on the arrest of the accused masterminds of the Bosnian genocide, in particular Ratko Mladic and Radovan Karadzic."
The group urged President Bill Clinton and other leaders to "summon the political courage to ensure that Nato troops arrest and surrender indictees." If they don't, "this first effort at an international system of justice since Nuremberg and Tokyo will fail."
The Serbian and Bosnian Serb authorities have shown no signs of extraditing anyone to the United Nations court, and Tadic's acquittal on all nine counts of murder because of lack of evidence suggests that the tribunal will find it very difficult to convict others on the most serious charges.
The Foreign Office said the verdict marked "a further step in bringing to justice those responsible for crimes against humanity".
It added that the United Kingdom wanted to see "all those responsible for war crimes brought to trial in The Hague".