BELGRADE, Serbia » He has spent 15 years on the run, sometimes in plain sight at soccer matches and weddings and sometimes deep in the fabric of this secretive city. Now, Europe’s most wanted war crimes suspect, Ratko Mladic, is being hidden by no more than a handful of loyalists, most probably in a neighborhood of Communist-era housing towers, according to investigators and some of his past associates.

The diminished circumstances of the former Bosnian Serb general, who once was protected by scores of allies and Serbian government officials, make him ripe for capture, these people say. But a softening by several European countries on whether his arrest should be a prerequisite for Serbia’s admission to the European Union is raising questions about whether he will ever face justice.

These developments make this a seminal moment not only in the search for Mladic but also in Europe’s often agonized deliberations over how much to encourage the manhunt in the face of deeply conflicting priorities. In the name of European unity and stability, should Europe put a premium on rehabilitating a battered country that became a pariah state as Yugoslavia broke apart in the Balkan wars of the ’90s?

Or, in the name of its human rights tradition, should it first require a now-friendly Serbian government to make the politically difficult arrest of a man blamed for the worst ethnically motivated mass murder on the Continent since World War II? That involved the massacre of 8,000 Muslim men and boys from the Bosnian town of Srebrenica.

Until now, Serbia’s hopes of joining the European Union have been thwarted by a firm insistence that Mladic be handed over for trial at The Hague. But time has played its hand. The vividness of the wartime horrors has receded outside the Balkans. Mladic has aged, and, according to many sources, is sick and more isolated, probably moving from nondescript apartment to nondescript apartment in the sprawling New Belgrade development.

The two-year-old government under President Boris Tadic has been overtly pro-Western and has vowed to apprehend Mladic. But he has nonetheless evaded arrest even after a fellow fugitive, former Bosnian strongman Radovan Karadzic, was brought in.

There are strong indications that when European foreign ministers meet in Luxembourg on Monday, the balance could tip away from requiring an immediate arrest, allowing Serbia to begin an admission process that some in Europe consider crucial to stability in the Balkans.

"Your future is the European Union, and that future must accrue as soon as possible," the Greek prime minister, George Papandreou, said in Belgrade this month, in a comment echoing others made by officials from France, Germany and Belgium.

Secretary of State Hillary Rodham Clinton has also offered encouragement.

But some senior European officials and human rights groups are unrelenting in believing that a compromise over Mladic would undermine international law and amount to a moral failure.

"The arrest should be a No. 1 priority," Serge Brammertz, the chief prosecutor of the International Criminal Tribunal for the Former Yugoslavia, said in an interview.

He was one of many speakers and world leaders at a 15-year commemoration of the Srebrenica massacre this summer to call for a quick capture.

"I said in Srebrenica at the summer memorial that this was the most emotional moment for me in my three years with the tribunal," he recalled. "I could see that for all of the survivors and relatives, Srebrenica is not an event from the past."

Dutch diplomats say they are now the lone holdouts for an arrest as a prerequisite for European Union membership. They are hoping to forestall action until December, when Brammertz issues his annual report evaluating Serbia’s effort in the manhunt.

Mladic, a burly man with a ruddy face and sharp blue eyes, has proved a wily adversary — tough, resourceful and abetted by protectors with military training, according to more than two dozen sources. Among them are government investigators; two loyalists who aided him and Karadzic; and five family friends, including the family priest.

In 1992, one month after a Bosnian majority voted to secede from Yugoslavia, Mladic’s Bosnian Serb forces began a 3 1/2-year siege of Sarajevo, killing 10,000 people, including 3,500 children. In 1995, the men and boys of Srebrenica were led to killing fields where they were shot with hands bound.

That year an international court in The Hague indicted Mladic on charges of war crimes in the Sarajevo siege and genocide in the Srebrenica massacre. He became a fugitive at a time when 60,000 NATO troops were in the Balkans, raising questions about why he was not seized. U.S. and European diplomats say a consensus prevailed that no country wanted to spill its soldiers’ blood in a battle with Mladic’s armed protectors.

For years, he did not bother to lie low. Protected by Yugoslavia’s nationalist president, Slobodan Milosevic, he enjoyed a Chinese-Yugoslav soccer match surrounded by bodyguards at a Belgrade stadium in 2000. He prayed at his brother’s funeral in 2001 in a jogging suit and sunglasses with a young woman clasping his arm, according to the family priest, Vojislav Carkic.

One protector — a Serbian military officer who was later arrested — recalled that Mladic lived fairly openly in a house guarded by a private 52-man security detail with four cars.

His situation began to shift after a popular uprising in October 2000 led to Milosevic’s ouster. In 2001, a new government, threatened with the loss of U.S. aid and World Bank loans, arrested Milosevic on genocide charges and sent him to The Hague.

Mladic, 68, pulled back from public view and began to move among military barracks, according to friends, who said they would visit him to play table tennis or chess. As he did, the myth of his fugitive cunning only grew.

In 2002, the government signed a cooperation agreement with the war crimes tribunal in The Hague. It eventually asked him to leave the barracks in Belgrade where he had been hiding. According to Vladimir Vukcevic, Serbia’s war crimes prosecutor, he simply refused.

Nonplussed, the military authorities eventually smoked him out by summoning a police helicopter to hover over the barracks to pretend a raid was imminent. But that did little more than provoke Mladic to speed away.

There were other attempts to close in on the fugitive. In March 2003, the Serbian prime minister, Zoran Djindjic, pledged to arrest him to pave the way for admission to the European Union. Days later, a sniper killed Djindjic.

One protector described how, as Mladic was forced to go underground, members of his network met routinely in crowded places, discarding phones and SIM cards 2 1/2 miles from their gatherings and discussing logistics by exchanging written messages, which they then burned.

Later, even when investigators had political backing to go after Mladic, they faced an insidious force that often undid their efforts — an elaborate "snitch culture" in which officials in military and state intelligence regularly tipped off Mladic operatives.

Perhaps with such insight, Mladic visited his dying mother’s bedside in 2003, Carkic, the family priest, related, and then vanished hours before investigators arrived.

The government’s boldest move took place in 2006. In raids on homes and hangouts, the government arrested more than a dozen protectors. The actions damaged the network, but there is a belief that they, too, actually worked to help Mladic, making him aware that pressure was increasing.

After the arrests, Mladic was still at large but was reduced to an ascetic existence in the large, gray towers of the sprawling New Belgrade apartment complex, where he could disappear like a ghost.

A former member of the government’s surveillance operation said investigators knew the hiding places of Mladic and Karadzic until February 2008. But the surveillance team was not told to try an arrest. He said the teams stalked both men outside their apartments and followed their helpers on grocery trips.

Investigators say Mladic’s network is now likely down to one or two deeply loyal associates, with probable links to the former Yugoslav Army — who aid him in a way roughly parallel to the way Karadzic was helped. One of Karadzic’s allies said he shifted among a collection of 12 apartments in New Belgrade, according to one protector, and survived monthly on about $280, for groceries, including fresh salmon.

The authorities now say that regardless of how the European Union treats Serbia’s application, they will press for an arrest.

"Serbia will bring its international obligations to completion," Tadic, Serbia’s president, wrote in response to written questions.

But Western officials say they have detected a long-running pattern: Whenever pressure increases, the Serbs make limited concessions. When pressure recedes, efforts evaporate. The authorities staged raids aimed at Mladic in 2008, for example. But in interviews Serbian investigators and protectors of Mladic and Karadzic said members of Serbian state intelligence services knew Mladic was hiding elsewhere.

"This game has been going on now for five to six years," said one Western diplomat, who declined to be named because he was not authorized to speak, and who cited suspicions that Mladic was ill. "They are either waiting for him to die — a stroke or kidney problems — or hoping to get into the European Union without doing anything."

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