According to the historian James William Parkes, during the 1st century after the Arab conquest (640–740), the caliph and governors of Syria and the Holy Land ruled entirely over Christian and Jewish subjects. He further states that apart from the Bedouin in the earliest days, the only Arabs west of the Jordan were the garrisons. The Arab garrisons were kept apart in camps, and life went on much as before for the local population. The taxes instituted were the kharaj—a tax that landowners and peasants paid according to the productivity of their fields—as well as the jizya—paid by non-Muslims in return for protection under the Muslim state and exemption from military service. The Byzantine civil service was retained until a new system could be instituted; therefore, Greek remained the administrative language in the new Muslim territories for over 50 years after the conquests.