 After the battle Umar changed his policy towards Sassanid Persian Empire, Yazdegerd III, who unlike his Roman counterpart Heraclius, denied submission to Muslim supremacy in his land, was a constant threat for Caliphate, Umar decided to launch a whole scale invasion of Sassanid Persian Empire to eliminate this threat.After a devastating defeat at Nihawand, last Sassanid emperor Yazdgerd III, a man with iron nerves, was never to be able again to raise more troops to resist the mighty onslaught of Umar, it had now became a war between two rulers, Umar will follow Yazdgerd III to every corner of his empire either will kill him or will capture him, like he did with Hormuzan.Yazdgerd III would have a narrow escape at Marv when Umar’s lieutenant was to capture him after Battle of Oxus river, he would save his life only by fleeing to China, far enough from reach of Umar, thus effectively ending the 400-year-old Sassanid dynasty.