(lieutenant) in the 3rd Regiment of the Tiroler Kaiserjäger (mountain infantry). In 1903, Phleps was transferred to the 11th Feldjäger (rifle) Battalion in Güns (in modern-day Hungary), and in 1905 was accepted into the Theresian Military Academy in Wiener Neustadt. He completed his studies in two years, and was endorsed as suitable for service in the General Staff. Following promotion to Oberleutnant (first lieutenant) he was transferred to the staff of the 13th Infantry Regiment at Esseg in Slavonia, then to the 6th Infantry Division in Graz. This was followed by a promotion to Hauptmann (captain) in 1911, along with a position on the staff of the XV Army Corps in Sarajevo. There, he specialised in mobilisation and communications, in the difficult terrain of Bosnia and Herzegovina. World War I At the outbreak of World War I, Phleps was serving with the staff of the 32nd Infantry Division in Budapest. His division was involved in the early stages of the Serbian campaign, during which Phleps was transferred to the operations staff of the Second Army. This Army was soon withdrawn from the Serbian front and deployed via the Carpathian Mountains to the Austro-Hungarian province of Galicia (modern-day Poland and Ukraine), to defend against a successful offensive by the Russian Imperial army. The Second Army continued to fight the Russians in and around the Carpathians through the winter of 1914–1915. In 1915 Phleps was again transferred, this time to Armeegruppe Rohr commanded by General der Kavallerie (General) Franz Rohr von Denta, which was formed in the Austrian Alps, in response to the Italian declaration of war in May 1915. Armeegruppe Rohr became the basis for the formation of the 10th Army, which was headquartered in Villach. Phleps subsequently became the deputy quartermaster of the 10th Army, responsible for organising the supply of the troops fighting the Italians in the mountains. On 1 August 1916, Phleps was promoted to Major. Later that month, King Ferdinand of Romania led the Kingdom of Romania in joining the Triple Entente, subsequently invading Phleps' homeland of Siebenbürgen. On 27 August, Phleps became the chief of staff of the 72nd Infantry Division, which was involved in Austro-Hungarian operations to repel the Romanian invasion. He remained in this theatre of operations for the next two years, ultimately serving as the chief quartermaster of the German 9th Army, and was awarded the Iron Cross 2nd Class, on 27 January