I have a friend whose uncle died in the Bulgarian army's siege of Erdine in the First Balkan War of 1913. A fellow soldier on the battlefield found a spent artillery shell near the uncle's body - presumably the one that killed him. The soldier brought the shell back to my friend's family. It was passed down until my friend inherited it. Now he keeps the shell in his bedroom.

When my friend finished telling me this story, tears welled up in his eyes. He held up the shell, a brass metal casing that looks deceptively harmless. "This is Bulgaria," he said.

Since 2006, the date of Bulgaria's capture of Erdine - March 26 - is an official holiday called Thrace Day. But its less a day to remember the battle, though in military and church circles that's still done, than a time to consider how to integrate south-eastern Bulgaria - as well as parts of Greece and Turkey - into Europe in general. It's a fitting commemoration, memories of a day of violence marshalled for reconciliation.

The prime mover behind Thrace Day was the Sofia-based Union of Thracian Societies. They successfully lobbied the Cabinet to proclaim the holiday. They hope to make it a national holiday when people get the day off from work.

Founded more than 100 years ago as an organisation to bring together more than 200 groups that had sprung up to celebrate Thracian culture, the union now has thousands of members, said Konstantin Karamitrev, its chairman. Karamitrev estimates there are 800 000 Bulgarians living in the Thracian region.

It's important to note, however, that when Karamitrev talks about Thrace, he is not talking about ancient Thrace, the civilisation that flourished three millennia ago and which produced the gold artefacts on display in the National Museum of History in Boyana. When the union's chairman identifies Bulgarians, Greeks or Turks as Thracians, he refers merely to those people living in the region where the three countries abut each other near the Bosporus.

"Thrace is a geographical place in Bulgaria, Greece and Turkey. We never put forward a proposal to unify these lands," he said. "Our strategy is to integrate all of Thrace into the European Union and to preserve it and deal with its economic development."

But while Karamitrev acknowledges that contemporary Bulgarians are not directly linked to ancient Thracians, he is quick to note that Bulgarians today are in a sense the heirs of Thrace. It is their patrimony. Certainly Bulgarians are responsible for safeguarding remnants of ancient Thrace on Bulgarian territory.

"The organisation was created mainly to protect Thracian cultural heritage," he said. "We are proud that Thracian cultural history is among the most ancient in Europe. Centuries before Christ, one of the most ancient civilisations was here. They developed crafts, a military, industry."

In January last year, at a union event in Stara Zagora, President Georgi Purvanov lent more political backing to Karamitrev and his colleagues' plans. "Studying and popularising Thrace's cultural and historical heritage is a priceless resource for sustainable cultural, economical and social development," Purvanov said, according to a media statement.

The Union of Thracian Societies and Thrace Day in many ways are recent examples of Bulgarian patriotism, which should be distinguished from its less amiable cousin, nationalism. The union holds events for children to learn about Bulgarian history, erects monuments and publishes reports outlining economic prospects in the Thracian region, many of which centre around tourism that includes folk exhibitions and ancient monuments.

"We entered the EU and deserved it because of our cultural heritage," Karamitrev said.

But its hard for Karamitrev to abandon Balkan antagonisms entirely. The union wants to erect a statue of its founder, Captain Petko Voivoida, in the village where he was born, for example. There's only one problem. The village is now in northern Greece, and local officials won't accept the statue. Instead, a resident allowed the union to put the statue up in his private property.

"Rome put (a statue of Voivoda) up in city centre because he helped with the Italians in Crete against the Ottomans," said Karamitrev, who believes the Greeks just don't want to admit a hero from their village was Bulgarian.

"The views, wishes and desires of Greeks - I mean ordinary Greeks and Greek statesmen - their view is that everything Thracian is theirs," he said. "For centuries they have been implanting this sense of chauvinism."

The status of Turkey in Europe is also a complicated question for Karamitrev. "Our official position is that Turkey is an Asian country," he said. "It stepped in Europe and took East Thrace for itself. The whole European part of Turkey was stolen property. Bulgarian people lived there and had to move out."

Turkey stole properties belonging to Bulgarians in land that is now Turkish, Karamitrev said. He doesn't want the EU to even consider Ankara's membership until that dispute is settled. The Union of Thracian Societies has a petition with Brussels seeking for these claims to be redressed, he said.

Whether that petition will be successful is unclear. Without question, however, is that Thrace's profile as a cultural and economic region will rise in the years ahead.