At the outbreak of World War I, was incapacitated in consequence of an accident, but was able to play a part in the Battle of Soissons. He became the commanding general of the 10th Army on 21 January 1915, which he would command until 5 March 1918. This Army engaged in the great battle of the Masurian Lakes in February 1915. In August, he took Kovno and afterwards the fortresses of Grodno and Olita, and continued his advance into Russia. He received the on 18 August 1915 and the oak leaves to the on 28 September 1915. On 30 July 1916, while remaining in command of the 10th Army, became supreme commander of Army Group Eichhorn (') based around 10th Army, which he would command until 31 March 1918. On 18 December 1917, was promoted to . On 3 April 1918, Field Marshal became supreme commander of Army Group Kiev (') and simultaneously military governor of Ukraine.