A former Bosnian Serb leader was found guilty of genocide and other charges on Thursday for his role in deadly campaigns during the Bosnian war in the 1990s, including the massacres of thousands in Srebrenica, as an international tribunal announced a long-awaited reckoning in Europe’s bloodiest chapter since World War II.

Radovan Karadzic was found guilty of 10 charges that touched on many of the atrocities and ethnic-cleansing policies that stunned the world as Bosnia became a crucible for the rivalries and fears that tore apart Yugoslavia.

Central to the case was Kara­dzic’s role in the worst systematic slaughter of the war: the slayings of 8,000 Muslim men and boys outside the Srebrenica enclave near the close of the three-year Bosnian conflict.

Karadzic, 70, was sentenced to 40 years in prison by the International Criminal Tribunal for the former Yugoslavia, which is nearing the end of its investigations of alleged atrocities and other crimes from the country’s meltdown. In total, more than 100,000 people died in the three-sided Bosnian conflict among Bosnian Serbs, ethnic Croats and Muslims.

The court’s ruling placed widespread blame on Karadzic, who it said directed murders, purges and other abuses against civilians, including the 44-month siege of the Bosnian capital, Sarajevo, in which Serb gunners and snipers fired nearly daily from surrounding ridges.

Karadzic — a Bosnian Serb political leader and commander of military forces — claimed he was seeking only to protect ethnic Serbs during the war. A legal adviser to Karadzic said he will appeal the court ruling.

The proceedings of the tribunal at The Hague, which is backed by the United Nations, have been closely watched as a potentially significant step in applying international law to investigations of alleged war crimes and other abuses against civilians.

“This is a momentous day for international justice, but also for those in Bosnia who lost husbands and wives, sisters and brothers, sons and daughters in a coordinated campaign of violence,” said Susannah Sirkin, director of international policy and partnerships at Physicians for Human Rights, a group that was involved in exhuming remains from some of Srebrenica’s mass graves.

Karadzic — who was indicted in 1995 but was on the run until his capture in 2008 — was the most senior Bosnian Serb figure to face prosecution at the court, which has spent more than two decades probing the conflicts in the former Yugoslavia.

The trial revisited the horrors of Srebrenica, in which Bosnian Muslims were herded from U.N.-designated “safe havens” into killing fields over several days in July 1995 and their bodies dumped into shallow pits. Investigators later uncovered many bodies with their hands still bound behind their backs and shots to the backs of their heads, evidence of execution-style ­slayings.

At a U.N. meeting last year marking the 20th anniversary of the slaughter, Deputy Secretary General Jan Eliasson said the atrocities will remain a stain on the world body.

“We gather in humility and regret,” Eliasson said, “to recognize the failure of the United Nations and the international community to prevent this tragedy.”

Still awaiting trial are Kara­dzic’s military chief, Gen. Ratko Mladic, and ethnic Serb political firebrand Vojislav Seselj.

In 2006, former Serbian president Slobodan Milosevic died in his cell at The Hague before judges could deliver verdicts in his trial.

Karadzic was among the most-wanted fugitives from the Balkan wars. When he was captured in Belgrade in 2008, he was posing as a New Age healer — with a beard, shaggy hair and oversize glasses — and using the alias Dragan Dabic.

The Karadzic convictions could serve to strengthen the credibility and reach of other international tribunals, including the International Criminal Court. On Monday, the ICC convicted a former Congo militia leader of war crimes carried out in the neighboring Central African Republic.

But some believe it is too soon to judge whether pan-national courts can adequately hold war criminals accountable.

“We must redouble our efforts to ensure that the prosecution of Radovan Karadzic does not stand as an isolated island of accountability in a sea of impunity,” said Nancy Combs, a professor at the College of William and Mary Law School and specialist in international criminal law.

After the verdicts on Thursday, the top U.N. human rights official, Zeid Ra’ad al-Hussein, said the decisions also send a wider message about the dangers of nationalism and ethnic vilification.

In a statement, he said the trial “should give pause to leaders across Europe and elsewhere who seek to exploit nationalist sentiments and scapegoat minorities for broader social ills.”

Read more:

Look back at Srebrenica

Gallery: Gen. Ratko Mladic at The Hague

Images of Bosnia now and then

Today's coverage from Post correspondents around the world