In April 1915, the 1st Expeditionary Force under the command of Halil Bey moved towards northern Persia. The objective was the city of Dilman, and to clean this region from Nazarbekov's forces, which would provide a significant tactical advantage in the Caucasian Campaign. Diliman was the place of one of the fiercest battles between the Armenians and the Turks. The first battalion of the Armenian volunteers, under the command of the Andranik repulsed the attacks of Khalil Bey, until the Russian Chernozubov arrived The newly arrived Russian forces from the Caucasus, they were able to put to flight Khalil Bey. A poorly executed night raid on April 14 cost Halil Bey around 2,000 casualties. He lost 3,600 soldiers in the course of those three days. General Nazarbekov managed to push Halil Pasha regulars towards Başkale after the Battle of Diliman (April 15, 1915), securing the situation. Halil Bey received the following cable from Enver Pasha and leave this theater of war: "Van is silenced. Roads to Bitlis and Iraq are under danger. In order to avoid even greater threats, withdraw as soon as possible and join the Third Army which would take control of these gateways."