 In June 1913 Serbia and Greece signed a defensive pact (Greek-Serbian Alliance of 1913) opposing to Bulgaria's expansionist goals.Eventually on 16 June of the same year Bulgaria attacked both countries, starting the Second Balkan War.Being decisively defeated by the Greeks in the Battle of Kilkis-Lahanas and by the Serbs in the battle of Bregalnica, Bulgaria retreated into defensive positions until Romania entered the war by attacking Bulgaria and threatening Sofia, resulting in the latter's defeat.