The last king of the line of _Sassanids_, _Yezdegerd III_., having lived for many years as a fugitive, perished by the hand of an assassin (652). Meantime _Egypt_ had submitted to the irresistible invaders under _Amr_, who was aided by the Christian sect of the _Copts_, out of hostility to the Greek Orthodox Church. After a siege of fourteen months, _Alexandria_ was taken; but it is probably not true that the library was burned by _Omar's_ order. In the disorders of the times, the great collections of books had probably, for the most part, been dispersed and destroyed. Six friends of Mohammed, selected by _Omar_, chose _Othman_ (644-656) for his successor, who stirred up enmity by his pride and avarice. Under him the Christian _Berbers_ in Africa were won over to the faith of Islam, and paved the way for its further advance. THE OMAYYADS: CONQUEST OF AFRICA AND SPAIN.--_Othman_ was assassinated by three fanatics, and _Ali_ was then raised to the caliphate; but _Muawiyah_, representing the family of the _Omayyads_, made himself the head of an opposing party, and, after the assassination of _Ali_, became sole caliph (661). He removed the seat of the caliphate to _Damascus_. He carried the Arabian conquests as far as the _Indus_ and _Bokhara_. He created a fleet on the Mediterranean, under an "Admiral," that is, a commander on the sea. In seven successive years he menaced Constantinople with his navy. At a later time, in 717, under the caliph _Soliman_, another great attempt was made on the capital of the Greek Empire. With an army of a hundred and twenty thousand men, he traversed Asia Minor and the Hellespont, and was supported in his attack by a fleet of eighteen hundred sail. But the energetic defense, which was aided by the use of "the Greek fire,"--an artificial compound which exploded and burned with an unquenchable flame,--caused the grand expedition to fail; and the Eastern Empire had another long lease of life. The successors of _Muawiyah_ accomplished the subjugation of Africa. They were invited by the native inhabitants, who groaned under the burdens of taxation laid on them by the Greek emperors. About A.D. 700 the Arab governor, _Musa_, completed the conquest of the African dominion of the Greeks as far as the Atlantic. The amalgamation of the _Berbers_ with the other inhabitants of that region, and with the _Arabs_, resulted in the race called _Moors_. At this time the Spanish Visigothic kingdom, which had become Catholic (586-601), was much enfeebled, and a prey to discord. Under _Tarik_--from whom _Gibraltar_, or the mountain of _Tarik_ near which he landed, is named--the Arabs crossed into Spain, and for the first time found themselves face to face with the barbarians of the North. In the great battle of _Xeres de la Frontera_, near the _Guadalquivir_, in 711, which lasted for three days, the fate of the Visigothic kingdom was decided. Eight years were occupied in conquering Spain. In 720 the Saracens occupied _Septimania_ north