Patricia Crone 
From Arabian Tribes to Islamic Empire [PDF ebook] 
Army, State and Society in the Near East c.600-850

This second collection of articles by Patricia Crone brings together studies on the development of early Muslim society, above all the army with which it was originally synonymous, from shortly after the Prophet’s death until the mid-Abbasid period. The focus is on the changes that the Arab tribesmen underwent thanks to settlement outside Arabia, their strained relations with converts from the conquered population, and their gradual eclipse by them.