On 25 October 1915, Sakharov became the commander of the 11th Army, which operated under the command of the Southwestern Front. Under his command, the 11th Army participated in the Brusilov Offensive in 1916. On 19 October 1916 he took command of the Danube Army, which the Imperial Russian Army had created to provide assistance to Romania during the Romanian Campaign. After the Imperial Russian Army created the Romanian Front based on the Danube Army and the remnants of the Romanian Army, Sakharov was appointed assistant to the commander-in-chief of the Romanian Army, King Ferdinand I of Romania, on 12 December 1916.