Radovan Karadzic is accused of ordering "ethnic cleansing"
The arrest of Radovan Karadzic has given Hague Tribunal prosecutors the chance to win a landmark case against a man accused of orchestrating the horrors of the Bosnian war.
The tribunal has already jailed generals, warlords and paramilitary thugs in cases that have revolutionised international justice, but it has yet to convict one of the masterminds.
Many think that chance was missed with the case of former Yugoslav President Slobodan Milosevic.
Accused of orchestrating three separate wars in Bosnia, Croatia and Kosovo, Milosevic's trial dragged on so long - four years - that in March 2006 he died of heart failure before it could finish.
For supporters of the court, the arrest of Mr Karadzic gives prosecutors a second chance.
The crimes the former Bosnian Serb president is accused of ordering are already seared into the public consciousness.
First is the siege of Sarajevo, where about 12,000 people, including 1,000 children, were killed by indiscriminate Serb shelling and sniper fire.
Eleven counts of genocide, war crimes, crimes against humanity and other atrocities
Charged over shelling Sarajevo during the city's siege, in which some 12,000 civilians died
Allegedly organised the massacre of up to 8,000 Bosniak men and youths in Srebrenica
Targeted Bosniak and Croat political leaders, intellectuals and professionals
Unlawfully deported and transferred civilians because of national or religious identity
Destroyed homes, businesses and sacred sites
Then there are charges that he set up the camps into which Bosnian Muslims (Bosniaks) were herded to be tortured, starved and killed.
And thirdly is the 1995 massacre at Srebrenica, where Serb forces rounded up and killed up to 8,000 unarmed Bosniak men and boys, burying their bodies in mass graves in forests around the town.
Mr Karadzic is accused of ordering these crimes as part of a plan to "ethnically cleanse" Bosnia. In the war Serb extremists expelled non-Serbs from areas they considered to be Serb territory.
Proving the atrocities themselves will be the easy part: the horrors of the Bosnian war have already been copiously documented in earlier trials.
Convictions came after prosecutors wove a complex tapestry of evidence combining eyewitnesses, radio intercepts, satellite photographs, captured Serb documents and DNA taken from mass graves.
More difficult may be pinning the crimes on Mr Karadzic, who may argue that as the civilian head of his self-proclaimed state, he had no control over the army.
Prosecutors insist he shared responsibility with his former army commander, Ratko Mladic, indicted on many of the same charges, and still at large in Serbia.
Particularly difficult may be proving the most serious accusation, that of genocide.
Sarajevo was under siege for nearly four years
Nicknamed the "crime of crimes", genocide is a difficult charge to make stick because it requires proof not just of atrocities, but that these atrocities were part of an attempt to "destroy in whole or in part" a specific group - in other words, prosecutors have to get inside the mind of the accused.
Hague judges have already ruled that ethnic cleansing, despite its brutality, did not amount to genocide, because the intention was to deport rather than annihilate the Bosniaks.
Only with Srebrenica have they agreed genocide took place. But even here the only two genocide convictions, of former Serb army officers, were for the lesser offences of complicity or aiding and abetting genocide.
But prosecutors are confident that with Mr Karadzic, they will secure a full-blown genocide conviction, arguing that he was the architect of the slaughter.
Easing the workload for the court, the UN has already decided that the court's 2010 closure date will be extended to allow trials of Mr Karadzic and other indictees to finish.
Mr Karadzic, facing a possible life sentence if convicted, is unlikely to make it easy for the prosecutors, having said that he plans to run his own defence.
Milosevic did the same thing, as was his right, causing serious delays to proceedings.
Rights groups meanwhile see a political dimension to the case, hoping that if it goes well it will persuade sceptical world leaders that war crimes justice is a cause worth backing.
Bosnian Serb forces waged a brutal campaign against Bosniaks and Croats
Mr Karadzic is not the only high-profile defendant on trial in The Hague. A few miles away, in premises rented from the International Criminal Court, the Sierra Leone Special Court is trying former Liberian President Charles Taylor on charges that equal Mr Karadzic's for brutality.
Former Hague tribunal prosecutor Richard Goldstone once described the international community as his "arms and legs", arguing that without the backing of world leaders, he was powerless to secure the arrest of top suspects.
It was these "arms and legs", in the form of pressure from the European Union, that helped drive Serbia to arrest Mr Karadzic.
But critics say such pressure is missing in the case of Sudan, where the United Nations has refrained from sanctions to force Khartoum to hand over its president, Omar al-Bashir, accused last week by International Criminal Court prosecutors of genocide.
Good results in the Karadzic and Taylor cases will, rights groups say, be a powerful advertisement for the cause of international justice.
"Two good trials are needed," says Richard Dicker, director of international justice at New York-based Human Rights Watch. "By 'good trials' I mean a sharp posing of contradictory evidence. These international tribunals have worked, you can't make that point enough."
Chris Stephen is author of Judgement Day: The Trial of Slobodan Milosevic, published by Atlantic Books in 2004.