The critics of Islâm have indulged in many theories to explain the marvellous victories of the Moslems over such great powers as Byzantium and Persia. ‘Rhetorical expressions about the decaying condition of both empires and the youthful energies of the Moslems are unsatisfying to the inquirer who keeps the concrete facts before him.’[39] ‘Both Byzantium and Persia had at their command genuine soldiers regularly armed and disciplined. The traditions of Roman warfare were not yet entirely lost, and the Persians still possessed their dreaded cuirassiers, before whom, in better times, even the armies of Rome had often fled.... The Emperor Heraclius was certainly the greatest man who had held the empire since Constantine and Julian. He was an astute diplomatist, a very competent general, and, as a soldier, bold even to rashness.’ How was it then that ‘the wretchedly armed Arabs, fighting not in regularly organised military divisions, but by families and clans, and under leaders who never before had faced disciplined troops,’ shattered the armies of both Chosroes and Cæsar? And be it noted that in every battle—at Kâdessia, at Nehâwand, Yermuk, and Ajnâdin—they were outnumbered sometimes as six to one.[40] The Moslem explanation is Biblical in its simplicity: ‘God took the heart out of the polytheists.’ The Christian historian offers divers explanations, ‘yet the phenomenon continues mysterious as before.’[41] The conquest of Persia had brought to Medîna many Magian fanatics desirous of avenging on the Caliph the fall of their country. The simplicity of life led by Omar and the utter absence of guards and attendants favoured their design. One day, whilst sitting as usual in the mosque listening to the petitions of the people, he was attacked and mortally wounded by one of them. =Death of Omar, 644 A.C.=—His death was an irreparable loss to Islâm. His knowledge of the character of his people, his extraordinary breadth of vision, his sagacity and vigour of mind, enabled him to exercise an influence over the Arabs which none of his successors ever achieved. =Election of Osmân.=—An aged member of the family of Ommeya,[42] named Osmân, was now elected to the vacant chair. =His Death, 656 A.C.=—His partiality for and favouritism towards his kinsfolk gave rise to a mutiny in which he lost his life. =Conquest of Egypt under Osmân.=—During Osmân’s Caliphate Byzantine incursions from Alexandria into Syria had led the Moslem Government to despatch an expedition into Egypt, which completed its conquest in two battles. The addition of Northern Africa beyond Egypt was due to similar causes. The same destiny which led the English from Bengal to the Punjab, and still leads them on in Nigeria, led the Arabs from the confines of Egypt to the shores of the Atlantic.