The Battle Hostile_encounter of Kosturino was a World War I battle , fought Hostile_encounter between 6 and 12 December 1915 .

On December 6 , a Bulgarian troops attacked Attack the French and British-held trenches in Kosturino , at the time part of the Kingdom of Serbia ( present Presence day North Macedonia ) .

The Entente defeat Conquering at Kosturino led to Causation the complete withdrawal Escaping of Allied forces Causation from Serbia , thus enabling Preventing_or_letting the Central Powers to build Building the Berlin to Constantinople rail line .