 Complete the following phrase:  After the outbreak of World War I, when Jovan Babunski formed the Sava Chetnik detachment, which was then placed under the command of Major Vojislav Tankosić, Voskars unit went on to fight the Austro-Hungarians in the late summer of 1914 and later destroyed a railway bridge on the Sava River to prevent Austro-Hungarian forces from crossing it. It took the Austrians and the Central Powers three attempts at invading Serbia in late 1915 to reach their goal. During the Serbian armys retreat through Albania, the Montenegrin Army that protected the retreat of Serbian forces defeated the Austrians on 7 January 1916 in the 