BELGRADE, Serbia — More than a dozen years since NATO missiles tore through the Yugoslav Defense Ministry, the building's jagged remains still scar Belgrade's skyline.

The unreconstructed ruin is a potent symbol of the violent past and enduring tensions that have kept Serbia and its Balkan neighbors frozen out the European mainstream long after the wars that ripped Yugoslavia apart in the 1990s.

In government buildings across Kneza Milosa street from the bombsite, however, there’s new optimism that the Balkans are coming in from the cold.

"Countries in the region are firmly dedicated to European values and principles," says Stanislava Pak Stankovic, advisor to Serbian President Tomislav Nikolic. "It is important to move on because we were lagging behind for decades. We can grab the future by changing mindsets."

Two events this year have boosted hopes that 2013 could become a turning point for the region's fortunes.

In April, the government signed an agreement brokered by the European Union to normalize relations with the authorities in Kosovo — a territory Belgrade regards as a breakaway province, but which 105 countries, including the United States and 23 EU members, recognize as an independent state.

Three months later, Croatia was accepted as the 28th member of the EU, becoming the second former Yugoslav country to join the European bloc following Slovenia's entry in 2004.

Croatia's membership after seven years of negotiations was welcomed by others in the region for pointing the way ahead. It shows countries that emerged from the 1990s conflicts can overcome a post-war morass of corruption, political instability and ethnic tensions to secure a seat at Europe's top table.

Underscoring a new spirit of cooperation between former enemies, the Croatian government has promised to use its experience to help Serbia and others follow its path to the EU.

"There was a time when it was viewed as great if we got [EU membership] and our neighbors didn't. That has changed," Croatia's Foreign Minister Vesna Pusic recently said.

“It is almost impossible to achieve stability without stable neighbors," she told an international lawmakers' meeting in Croatia. "Having a stable house in an unstable neighborhood is not stability.”

Further underscoring the improving ties, Croatia's President Ivo Josipovic visited Belgrade in October for talks aimed at pushing forward cooperation projects that include even joint military training.

Serious problems do persist between the two countries, however. Each side refuses to drop rival genocide cases against the other at the International Court of Justice and there remain deep-seated disputes over minority rights.

Nevertheless, officials at EU headquarters in Brussels have been heartened by a new spirit of compromise, not least because the Serbian government elected in July 2012 comes from a hard-line nationalist background.

Prime Minister Ivica Dacic was spokesman for President Slobodan Milosevic in the 1990s and considered so close to the wartime leader he earned the nickname "little Sloba." Dacic's influential deputy Aleksandar Vucic is a former member of the ultranationalist Serbian Radical Party, notorious for cracking down on independent journalists while serving as information minister during the 1999 Kosovo war.

Once in power, however, Dacic and Vucic surprised EU diplomats by agreeing to reach out to Kosovo leaders whom the Serbs once denounced as terrorists.

"It was necessary to demonstrate ... that [Kosovo's Prime Minister] Hashim Thaci is not 'the dragon, the old serpent' that assaulted our heavenly kingdom, but an ordinary man, an opponent not mythical but political, with whom we can and have to talk," Dacic wrote in a recent guest post in the Financial Times.

"Thank God Serbia learns quickly. Since that initial meeting, I have had a dozen meetings with Thaci, and not one serious voice raised against it in Serbia," he added.

Those talks and the April agreement between Serbia and Kosovo prompted the EU in June to agree to open membership talks with Serbia next year. Neighboring Montenegro has already begun negotiations and Albania is hoping get the nod soon, although EU headquarters says it must first take further steps to tackle corruption and improve its judicial system.

Elsewhere in the Balkans, the scenario is less encouraging.

Macedonia has been locked in international limbo for years. Greece is blocking the country's progress toward closer ties with the EU until the country agrees to change its name, which Athens claims is a threat to a Greek province also called Macedonia.

EU diplomats are concerned the prolonged deadlock risks destabilizing the former Yugoslav republic.

But the region's biggest headache is Bosnia.

Almost two decades since the end of the war that killed an estimated 100,000, tensions between Muslim, Serb and Croat politicians have stymied reforms needed to bring the country in line with European norms.

Many fear Bosnian tensions could become a focus of instability that would risk undermining progress in the wider region.

"There’s absolutely no political movement, in fact it's stagnating in many ways," says Florian Bieber, director of the Center for South East European Studies at the University of Graz in Austria.

"The main problem in the region is that there isn't a clear prospect of how to overcome the crisis of Bosnia, no one has a good recipe,” he adds. “This continual Bosnian crisis creates a situation where the state is getting increasingly weak and it risks a negative spiral."

Even in countries where the economic benefits of joining the European mainstream are now seen to outweigh nationalist passions, old enmities frequently resurface.

Almost 80 percent of Serbs living in the north of Kosovo boycotted elections held this month as part of the normalization agreement, and the first round vote was marred by violence.

Croatian soccer star Josip Simunic is facing disciplinary action following a World Cup playoff last week during which he apparently led fans in chanting slogans used by the country's pro-Nazi government during World War II, when it was blamed for the murder of hundreds of thousands of Serbs and Jews.

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Concerns over simmering nationalist tensions have prompted the United States to lobby hard to ensure all the region’s countries remain on a European path.

"Every country that binds itself to the EU’s rules and institutions brings us closer to the goal of a Europe whole, free and at peace," Vice President Joe Biden wrote in the Financial Times after Croatia's EU entry. "Unfortunately, there are still some who cling to ethnic grievances, personal rivalries and a zero-sum approach to politics that holds back progress."

American diplomats in the Balkans are worried not only by the lingering nationalist demons, but also the perceived indifference of Western European governments focused on their own economic woes and lacking enthusiasm for any further EU expansion.

Opinion polls show large majorities in many EU countries are opposed to letting more countries in, worried about potential new economic burdens, sources of unwanted immigration and political tensions.

The EU's newest members view such mindsets with disquiet.

"There is still a danger of states failing," Croatia's Foreign Minister Pusic told NATO lawmakers last month. "Things can look stable on the surface, but sometimes that stability has shallow roots."