The Governor of Kufa, Ammar ibn Yasir, received intelligence of the Persian movements and concentration at Nahavand and reported them to Umar. Although Umar had expressed a desire for Mesopotamia to be his easternmost frontier, the concentration of the Persian army at Nahavand forced him to act. He now believed that as long as Persia proper remained under Sassanid rule, the raids into Mesopotamia would continue. Hudheifa ibn Al Yaman was appointed commander of the forces of Kufa, and was ordered to march to Nahavand. Abu Musa was to march to Nahavand from Busra, while Nouman ibn Muqarrin marched from Ctesiphon. Umar decided to personally take the army concentrated at Medina to Nahavand to assume overall command. The members of the Majlis al Shura, however, suggested that Umar should command the campaign from Medina, appointing an astute field commander for Nahavand. Umar acquiesced, appointing Mugheera ibn Shuba as commander of the forces concentrated at Medina, and Nouman ibn Muqarrin as commander-in-chief at Nahavand. The Muslim army first concentrated at Tazar, and then defeated the Persians at the Battle of Nahavand in December 642. Nouman died in the action, and, as per Umar's instructions, Hudheifa ibn Al Yaman became the new commander-in-chief. Thereafter, the Muslims captured the whole district of Hamadan, encountering only feeble resistance.