On the occasion of the 90th anniversary of the end of World War I, the military history museums of Bulgaria and Austria teamed up to show an Austrian audience the role that the Kingdom of Bulgaria had in the war as an ally of Austria-Hungary.

The name of the exhibition "The Unknown Ally - Bulgaria in World War I" says a lot about why Bulgaria and Austria have decided to organise the exhibition. The Kingdom of Bulgaria participated in World War I as an ally of Germany, Austria-Hungary, and Ottoman Turkey from October 1915 until September 1918. The four countries formed the so-called Central Powers (the name comes from the location of these countries). They fought against a number of countries led by France, Russia and the British empire, teamed as the Entente powers.

Bulgaria was the last to join the war on the side of the Central Powers against the Entente when, in 1915, Bulgarian troops invaded Serbia in a co-ordinated move with German and Austro-Hungarian forces.

However, today few people in Austria know of the role Bulgaria had in the war as an ally of Austria-Hungary. The exhibition opened in June this year and will continue until February 2010. Its opening coincided with the 130th anniversary of Bulgarian-Austrian diplomatic relations.

It features 124 exhibits provided by Sofia Military Museum, including uniforms, war decorations, weapons, enemy trophies, documents, photos, as well as a catalogue in which Bulgarian and Austrian historians present various aspects of the war.

Highlights of the exhibition are the battles Bulgarian troops fought near Thessaloniki and the offensive they started against Romania in 1916-1917, when Bulgaria regained control over the Dobroudja area.

Special attention is paid to documents related to the Armistice with Bulgaria from September 29 1918, also known as the Armistice of Thessaloniki, which marked the end of the war for Bulgaria. According to the armistice terms, close to 100 000 Bulgarian troops remained as hostages till the end of the war. Bulgaria was the first to sign an armistice with the Entente, quickly followed by the Ottoman empire and Austro-Hungary, with Germany doing so on November 11 1918.