By Mark Lowen
BBC News, Belgrade
Kneza Milosa - or Prince Milos Street - in the heart of Belgrade is a place of stark contrasts.
The heart of Belgrade provides stark reminders of the conflict
Rickety old trams vie for space with chauffeur-driven BMWs, which climb the hill towards the plush suburb of Dedinje.
And elegant ministry buildings and embassies stand next to the half-collapsed, burned-out shells of the former military headquarters, bombed intensively by Nato 10 years ago.
At the time, the Yugoslav government of Slobodan Milosevic was attempting to suppress an ethnic Albanian insurgency in its southern province of Kosovo.
Nato declared war on Yugoslavia, calling the situation a humanitarian catastrophe.
An intensive 78-day aerial bombing campaign followed until Milosevic withdrew his troops. The territory was placed under United Nations administration.
Nine years later, Kosovo's ethnic Albanian majority unilaterally declared independence from what is now Serbia, despite failing to obtain a UN Security Council resolution authorising the move.
Russia had threatened to veto it, united in opposition with its Orthodox ally Serbia. A modest wave of recognitions of Kosovo followed, led by the United States.
Serbia cried foul, calling the secession illegal. Furious Serb protesters set the US embassy in Belgrade alight.
As the flames died down, the new government of Boris Tadic vowed to fight on, calling for the International Court of Justice in the Hague to examine the matter.
Now, the hearings are beginning in the first ever case of territorial secession brought before the ICJ.
Thirty countries will present their oral arguments. The issue appears straightforward: did Kosovo's declaration of independence comply with international law?
But the discussions will be complex, with both sides engaging in a tug-of-war over the legal minutiae. Serbia is likely to say that UN Resolution 1244, which ended the Kosovan war, reaffirmed the territorial integrity of the then Yugoslavia, maintaining Belgrade's jurisdiction over its southern province.
It is thought the Kosovan side will argue that the resolution did not expressly prohibit secession and that human rights abuses committed in Kosovo by Milosevic's government gave the province the right to self-determination.
The verdict, after months of deliberation, will be advisory, not legally binding. So what is the point of it all, I asked Serbia's President Boris Tadic?
Most people within the international community - many even in Serbia - now believe that turning back the clock and annulling independence is unrealistic.
"This isn't about reintegrating Kosovo within Serbia," says Mr Tadic, in the opulent surroundings of the presidential palace.
"This isn't about the independence of Kosovo. It is about starting from a blank page to talk with good will to find a sustainable, compromise solution."
So Serbia is ready to return to the negotiating table. The problem is that Kosovo believes there's nothing to negotiate about. Pristina says it is independent and that's final.
"The history of the Balkans is all about fragmentation and partition. We've suffered a lot through that," adds Mr Tadic, referring to the break-up of Yugoslavia in the 1990s and the wars that followed.
"That's why we must find a totally different approach."
That conciliatory tone is part of the new attitude that the Serbian government is trying to present over Kosovo.
"We're no longer part of the problem", says Mr Tadic. "We're part of the solution."
The reason is clear: Serbia is desperate to get on the path to European Union membership. Brussels says it won't require Belgrade to recognise Kosovo - "something we will never do," says the president - but has demanded greater cooperation between the two if membership is to be considered.
And so Mr Tadic faces a difficult balancing act: placating Serbia's right-wing, still angry over Kosovan independence, while showing a "softly-softly" approach for Brussels.
So is the ICJ process simply an attempt to prove he's doing something - anything - to fight for Kosovo?
"This is not about an internal political game," he assures me. "It is about principles. We are defending our legitimate national interests like any other country would."
On the streets of Belgrade, Kosovo elicits mixed emotions. Many now feel resigned to the status quo.
"It's still the heart and soul of our nation," says Jelisaveta Djuric. "But I don't think we can change things. Far more powerful forces are pulling the strings."
Bojan, a sports science student, calls Kosovan independence "a criminal act." "People who did it in Kosovo can do it in Spain, in Russia - anywhere that a part of a country wants to break away", he warns.
One woman, Milena, says: "I've never actually been there, so the whole issue isn't very real for me. What's happened is tragic, but my priority now is that Serbia joins the EU and that people move on."
And that is why the Kosovo issue still matters to the wider world: numerous governments face similar challenges to their authority as that of Serbia.
Countries from Nigeria to Georgia and Cyprus to China, have refused to recognise Kosovan independence for fear of fanning secessionist flames within their borders.
And so they - and their separatist movements - will be watching this ICJ case very closely indeed to see whether the decision might affect what happens in their own backyards.