In 1915, the troops of the Central Empires routed the Serbian army and threatened the French expeditionary corps, which found itself besieged in Salonica. The Bulgarian armies occupiying Macedonia were faced with serious supply problems. Only one railway ran through the very mountainous area, along the Vardar southwards from Uskub, today Skopje. Supervised by German military engineers, they built 60cm gauge lines, one linking Gradsko to Prilep and Bitola, and another, very long one, originating from General-Hanti, in the suburbs of
