Honored by Muslims as the epitome of the just ruler, 'Umar, or Omar--the second caliph--is one of the greatest figures in early Islamic history. His rule (634-44 CE) laid the foundations of an empire that has since defined, both culturally and geographically, the heartlands of the Islamic world. Shibli Numani's classic account links the military conquests of the period with 'Umar's reforms in law, government and public administration. He describes...