Islam migrants ("Muhajirun"), Muhammad in Medina established his political and religious authority. The Constitution of Medina was formulated, instituting a number of rights and responsibilities for the Muslim, Jewish, Christian and pagan communities of Medina, bringing them within the fold of one community—the Ummah. The Constitution established: All the tribes signed the agreement to defend Medina from all external threats and to live in harmony amongst themselves. Within a few years, two battles took place against the Meccan forces: first, the Battle of Badr in 624 – a Muslim victory, and then a year later, when the Meccans returned to Medina,
Battle of al-Qādisiyyah and led a group of Mubarizuns, from his Syrian contingent who were also the veterans of Battle of Yarmouk, through the Sassanids' right center towards Rostam's headquarter. Rostam again personally led a counterattack against the Muslims, but no breakthrough could be achieved. At dusk, the two armies pulled back to their camps. On 18 November, Rostam wanted a quick victory, before more Muslim reinforcements could arrive. The Elephant corps was once again in the front of the Sassanid army, giving him the advantage. Pressing this advantage, Rostam ordered a general attack along the Muslim front, using his full force. All