On the orders of Umar, Sa'd ibn Abi Waqqas, commander of the Muslim army in Iraq, sent an army under Iyad ibn Ghanm to conquer the region between the Tigris and the Euphrates up to Urfa. In 639–640, Raqqa fell into Muslim hands, followed by most of Jazirah, the last base of the Eastern Roman Empire in the region, which surrendered peacefully and agreed to pay Jizya.