The history of Jerusalem during the Middle Ages is generally one of decline; beginning as a major city in the Byzantine Empire, Jerusalem prospered during the early centuries of Muslim control (637/38–969), but under the rule of the Fatimid caliphate (late 10th to 11th centuries) its population declined from about 200,000 to less than half that number by the time of the Christian conquest in 1099. The Christians massacred much of the population as they took the city, and while population quickly recovered during the Kingdom of Jerusalem, it was again decimated to below 2,000 people when the Khwarezmi Turks retook the city in 1244. After this, the city remained a backwater of the late medieval Muslim empires and would not again exceed a population of 10,000 until the 16th century.