Constans II. was sole emperor from 642 to 668, and his son and successor, Constantine IV., reigned from 668 to 685. They were both strong, hard-headed warrior princes, fit descendants of the gallant Heraclius. Their main credit lies in the fact that they fought unceasingly against the Saracen, and preserved as a permanent possession of the empire nearly every province that they had still remained Roman at the death of Heraclius. During the minority indeed of Constans II., Alexandria(20) and Aradus, the two last ports preserved by the Romans in Egypt and Syria were lost. But the Saracens advanced no further by land; the sands of the African desert and the passes of Taurus were destined to hold them back for many years. The times, however, were still dangerous till the murder of the Caliph Othman in 656, after which the outbreak of the first civil war among the Moslems—the contest of Ali and Moawiah for the Caliphate—gave the empire a respite. Moawiah, who held the lands on the Roman frontier—his rival’s power lying further to the east—secured a free hand against Ali, by making peace with Constans. He even consented to pay him a small annual subsidy so long as the truce should last. This agreement was invaluable to the empire. After twenty-seven years of incessant war the mangled realm at last obtained an interval of repose. It was something, too, that the Saracens were induced to pause, and saw that the extension of their conquests was not destined to spread at once over the whole world. When they realized that their victories were not to go on for ever, they lost the first keenness of the fanatical courage which had made them so terrible.