After the Ottoman conquest of Egypt in 923 / 1517, the local rulers of Mecca offered Sultan Selim I supreme power over Arabia for political and economic reasons. Consequently, the two most important Muslim cities, Mecca and Medina
– and with them the holiest places of Islam – became part of the Ottoman Empire, and the sultans took the title of Caliph
. Thus, for about 400 years the Ottoman sultans paid particular attention to giving their generous support to the holy sites.