The northern and eastern boundaries of the empire were at length secured. It was now necessary to punish the Arab tribes who had taken advantage of the Kimmerian invasion to harass the empire on the south. Esar-haddon accordingly marched into the very heart of the Arabian desert--a military achievement of the first rank, the memory of which was not forgotten for years. The empire at last was secure. The Assyrian king was now free to complete the policy of Tiglath-pileser by conquering Egypt. Palestine was no longer a source of trouble. Judah had returned to its vassalage to Assyria, and the abortive attempts of Sidon and Jerusalem to rebel had been easily suppressed. True to his policy of conciliation, Esar-haddon had dealt leniently with Manasseh of Judah. He had been brought in fetters before his lord at Babylon, and there pardoned and restored to his kingdom. It was a lesson which neither he nor his successors forgot, like the similar lesson impressed a few years later upon the Egyptian prince Necho. The Assyrian conquest of Egypt has been already described. The first campaign of Esar-haddon against it was undertaken in B.C. 674; and it was while on the march to put down a revolt in B.C. 668 that he fell ill and died, on the 10th of Marchesvan, or October. The empire was divided between his two sons. Assur-bani-pal had already been named as his successor, and now took Assyria, while Saul-sum-yukin became king of Babylonia, subject, however, to his brother at Nineveh. It was an attempt to flatter the Babylonians by giving them a king of their own, while at the same time keeping the supreme power in Assyrian hands.