The Byzantine dominion in the Levant known as the Diocese of the East, was one of the major commercial, agricultural, religious, and intellectual areas of the Empire, and its strategic location facing the Sassanid Empire and the unruly desert tribes gave it exceptional military importance.[21] The entire area of the former diocese came under Sassanid occupation between 609 and 628, but it was retaken by the Emperor Heraclius until its irreversible lost to the Arabs after the Battle of Yarmouk and the fall of Antioch.