A Serbian Dragoon regiment, part of the Allied army based in the Greek port of Salonika, are pictured riding to repel an attack by the Bulgarian army, October 1916. At the beginning of the war the Serbian army had successfully resisted invasion by the Austro-Hungarian Empire, however, a combined offensive by the Central Powers, including the newly allied Bulgaria, forced the Serbian government and army to escape into neighbouring Albania and exile in December 1915.