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Foundation by the Rashidun Caliphate (632–661)

The city was founded at the beginning of the Islamic era in 636 and began as a garrison encampment for Arab tribesmen constituting the armies of the Rashidun Caliph Umar. A tell a few kilometers south of the present city still marks the original site which was a military site. While defeating the forces of the Sassanid Empire there, the Muslim commander Utbah ibn Ghazwan erected his camp on the site of an old Persian military settlement called Vaheštābād Ardašīr, which was destroyed by the Arabs. The name Al-Basrah, which in Arabic means "the over watching" or "the seeing everything," was given to it because of its role as a military base against the Sassanid Empire. However, other sources claim the name originates from the Persian word Bas-rāh or Bassorāh meaning "where many ways come together."

In 639, Umar established this encampment as a city with five districts, and appointed Abu Musa al-Ash'ari as its first governor. The city was built in a circular plan according to the Partho-Sasanian architecture. Abu Musa led the conquest of Khuzestan from 639 to 642, and was ordered by Umar to aid Uthman ibn Abi al-As, then fighting Iran from a new, more easterly miṣr at Tawwaj. In 650, the Rashidun Caliph Uthman reorganised the Persian frontier, installed ʿAbdullah ibn Amir as Basra's governor, and put the military's southern wing under Basra's control. Ibn Amir led his forces to their final victory over Yazdegerd III, the Sassanid King of Kings.

In 656, Uthman was murdered and Ali was appointed Caliph. Ali first installed Uthman ibn Hanif as Basra's governor, who was followed by ʿAbdullah ibn ʿAbbas. These men held the city for Ali until the latter's death in 661.