 However, the collapse of the front line enabled the Allies to assault Bulgarian positions from multiple directions and eventually quell the last pockets of resistance.The Central Powers' defeat at the Dobro Pole played a role in the Bulgarian withdrawal from the war and opened the way for the subsequent capture of Vardar Macedonia.The 28 June 1914, assassination of Austro-Hungarian heir presumptive Archduke Franz Ferdinand precipitated Austria-Hungary's declaration of war against Serbia.