The Arabian aristocracy thus created was recognised by the whole Moslem world. The rank and stipend now assigned descended in the direct line of birth. Even rewards given for special gallantry in the field were heritable.[353] By making thus the revenues of Islam the heritage of the nation militant, their martial genius was maintained, and their employment perpetuated as the standing army of the Caliphate. The ennobled nation, pampered by indulgence, factious and turbulent when idle, were indeed too often a serious element of sedition and intrigue. But they were nevertheless the backbone of Islam, the secret of its conquests, and the stay of the Caliphate. The crowded harems multiplied the race with marvellous rapidity; and the progeny were, by Omar’s organisation, kept sedulously distinct, so as never to mingle with the conquered races. Wherever they went they formed a class distinct and dominant--the nobles and rulers of the land. The subject peoples, even if they embraced Islam, were of a lower caste; and as clients of some Arab chief or tribe, courted their patronage and protection. Thus the fighting nation was set apart for the sacred task of subjugating nations and of propagating Islam; and even after the new-born zeal of the Faith had to some extent evaporated, the martial fire of the Arabs as a whole and undivided people was, owing mainly to Omar’s foresight, kept alive in full activity for two centuries and a half. The nation was, and continued, an army mobilised; the cantonment, not the city, their home; their business, war and the camp;--a people whose hereditary calling it was to be ready to march on warlike expeditions at a moment’s notice. [Sidenote: Register of all Arabs entitled to a stipend.] To carry out this vast design, a Register had to be drawn and kept up of every man, woman, and child, entitled to a stipend from the State--in other words, of the whole Arab race employed in the interests of Islam. This was easy enough for the higher grades, but a herculean task for the hundreds of thousands of ordinary fighting men and their families who kept streaming forth from the Peninsula; and who, by the extravagant indulgence of polygamy, were multiplying rapidly. But the task was simplified by the strictly tribal composition and disposition of the forces. Men of a tribe, or branch of a tribe, fought together; and the several corps and brigades being thus territorially arranged in clans, the Register assumed the same form. Every soul was entered under the stock and tribe and clan whose lineage it claimed. And to this exhaustive classification we owe in great measure the elaborate genealogies and tribal traditions of Arabia before Islam. [Sidenote: The _Dewân_ of Omar.]