In December 636, Umar ordered Utbah ibn Ghazwan to head south to capture al-Ubulla (known as "port of Apologos" in the Periplus of the Erythraean Sea) and Basra, in order to cut ties between the Persian garrison there and Ctesiphon. Utbah ibn Ghazwan arrived in April 637, and captured the region. The Persians withdrew to the Maysan region, which the Muslims seized later as well.