The part they played in the capture of the city and their subsequent renown deserve a somewhat complete notice. The order took its origin in a long recognised Moslem rule, that when a people at war with Mahometans is summoned to make submission and refuses it may be enslaved, and that in such a case one fifth of the property captured should belong to the sultan. Christian captives fell within the limit of this rule. In practice, however, the sultans by no means considered themselves bound to restrict themselves to the prescribed one fifth. They held that as many of the children as the conqueror thought fit should be given over to him to be trained for the public, and especially for military, services. Accordingly, without regard to the fact that the parents had already surrendered one or more sons to the ruler, they were often called upon to furnish others. The demand for Christian children to be given up absolutely to the sultan was regular and methodic. No tithe or other tax required for the service of the Church was ever claimed with more regularity and insistence than this blood tax for the service of Islam. A formal examination of Christian children available for service was made every five years, when a Turkish inspector, at the head of a troop of soldiers and bearing an imperial firman of authorisation, visited the portions of the empire assigned to him. The registers of the churches were carefully examined to see how many children ought to be brought forward for inspection, and the priests, under the penalty of death, were bound to show a correct list. The boys selected were usually between the ages of ten and twelve years. Those were preferred who were distinguished either by their strength, intelligence, or beauty. In addition to these regular and legal contributions to the services of the state, it was the custom of the pashas, on returning from the provinces to bring presents of Christian children to their imperial master.