The Rashidun Caliphate defeated the Sasanian Empire at the Battle of al-Qādisiyyah in Iraq.
The Battle of al-Qadisiyyah (Arabic: , romanized: Marakah al-Qdisyah; Persian: , romanized: Nabard-e Qdisiyeh) was fought in 636 CE between the Rashidun Caliphate and the Sasanian Empire. It occurred during the early Muslim conquests and marked a decisive victory for the Rashidun army during the Muslim conquest of Persia.
The Rashidun offensive at Qadisiyyah is believed to have taken place in November of 636. At the time of the battle the Sasanian army was led by Rostam Farrokhzad, who died in uncertain circumstances during the battle. The collapse of the Sasanian army in the region led to a decisive Arab victory over the Iranians, and the incorporation of territory that comprises modern-day Iraq into the Rashidun Caliphate.Arab successes at Qadisiyyah were key to the later conquest of the Sasanian province of Asoristan, and were followed by major engagements at Jalula and Nahavand. The battle allegedly saw the establishment of an alliance between the Sasanian Empire and the Byzantine Empire, with claims that the Byzantine emperor Heraclius married off his granddaughter Manyanh to the Sasanian king Yazdegerd III as a symbol of the alliance.
The Rashidun Caliphate (Arabic: اَلْخِلَافَةُ ٱلرَّاشِدَةُ, romanized: al-Khilāfah ar-Rāšidah) was the first caliphate to succeed the Islamic prophet Muhammad. It was ruled by the first four successive caliphs (successors) of Muhammad after his death in 632 CE (AH 11). These caliphs are collectively known in Sunni Islam as the Rashidun, or "Rightly Guided" caliphs (اَلْخُلَفَاءُ ٱلرَّاشِدُونَ, al-Khulafāʾ ar-Rāšidūn). This term is not used in Shia Islam, as Shia Muslims do not consider the rule of the first three caliphs legitimate.The Rashidun Caliphate is characterized by a twenty-five-year period of rapid military expansion followed by a five-year period of internal strife. The Rashidun Army numbered more than 100,000 men at its peak. By the 650s, in addition to the Arabian Peninsula, the caliphate had subjugated the Levant to the Transcaucasus in the north; North Africa from Egypt to present-day Tunisia in the west; and the Iranian Plateau to parts of Central Asia and South Asia in the east. The four Rashidun caliphs were chosen by a small electoral body consisting of prominent members of the Quraysh tribal confederation called shūrā (Arabic: شُـوْرَى, lit. 'consultation').The caliphate arose out of the death of Muhammad in 632 CE and the subsequent debate over the succession to his leadership. Abu Bakr, a close companion of Muhammad from the Banu Taym clan, was elected the first Rashidun leader and began the conquest of the Arabian Peninsula. He ruled from 632 to his death in 634. Abu Bakr was succeeded by Umar, his appointed successor from the Banu Adi clan, who continued the conquest of Persia, eventually leading to the fall of the Sasanian Empire in 651. Umar was assassinated in 644 by a Persian slave and was succeeded by Uthman, a member of the Banu Umayya clan, who was elected by a six-person committee arranged by Umar. Under Uthman, the conquest of Armenia, Fars and Khorasan began.Uthman was assassinated by Egyptian rebels in 656 and succeeded by Ali, a member of Muhammad's Banu Hashim clan, who presided over the civil war known as the First Fitna (656–661). The war was primarily between those who believed Uthman was unlawfully killed, supporting his cousin and governor of the Levant Muawiyah, and those who believed his killing was deserved, supporting the caliph Ali. The civil war permanently consolidated the divide between Sunni and Shia Muslims, with Shia Muslims believing Ali to be the first rightful caliph and Imam after Muhammad, favouring his bloodline connection to Muhammad. Additionally, a third faction in the war believed both Ali and Muawiyah should be deposed and a new caliph elected by shura; this faction supported the governor of Egypt Amr ibn al-As. The war led to the end of the Rashidun Caliphate and the establishment of the Umayyad Caliphate in 661 under Muawiyah.