In 1914 Austria-Hungary commenced the First World War by attacking Serbia at the Balkan front. After just a few weeks Austria-Hungarian troops clashed with the numerically far superior Russian imperial army in the Battle of Galicia at the Eastern front. When Italy joined the conflict in May 1915 on the Allied side and deployed in strength at the Alpine front to the south, Austria-Hungary was already critically undermanned and faced serious recruitment shortfalls, which diminished the chances to exact an early defeat on any of the opponents, instead be confined to struggle in a two-front war at the periphery of its own territory. Consequently, the Austro-Hungarian Army lacked the initiative and the contributions at the Macedonian front (Salonikifront) were marginal. Nonetheless, when Romania entered the war on the Allied side in August 1916 at the southern tip of the Eastern front, Austria-Hungary acted promptly and concluded this stage in late 1916 and occupied large areas of Romania. The greater two-front war only ended after the separate peace with Russia in March 1918, which, after all, did not forestall the collapse of the imperial army in the course of summer and autumn.