Asia and Egypt as well were inhabited in early times by many wandering or nomadic tribes. A tribe dwelt in one locality while pasturage was good, and when it was exhausted, would move on to new fields. Sometimes the tribe in possession of one district would learn that other tribes were drawing near, and in an age when strangers were considered enemies, this would furnish sufficient pretext for starting out on the march again. Periods of unrest sometimes swept over vast areas; in such a time as this, perhaps, Asiatic tribes poured into Egypt. In her pitiable plight, the country lay an easy prey to such invaders, who Manetho tells us numbered a quarter of a million. It is said that they took possession without a battle. Just who they were or where they came from is not known. We now know that the Hittites invaded Babylonia during the reign of Samsu-ditana, the last king of the First Dynasty of Babylon, and that this was the indirect cause of the fall of this dynasty (about 1750 B.C.). Scholars are beginning to suspect that the invasion of Egypt at this time was either led by the Hittites or due to Hittite pressure back of the tribes in Syria-Palestine. Their kings were called Hyksos, and from a doubtful etymology of this name they are still styled the "Shepherd kings." The invading conquerors put many of the Egyptians to death, taking their wives and children into slavery. Worshipping gods of their own, they hated the gods of the Egyptians and destroyed many temples and monuments. Generally speaking, they remained in the Delta and the Fayoum, the Theban princes ruling in the south as their vassals. Gradually these fierce Asiatics took on the civilization of the land they had invaded. They donned Egyptian dress, spoke and wrote as the Egyptians, and built temples much like theirs. The country rallied from its recent disaster and life became not unlike that of earlier times. In time the Theban nobles increased in power; the Hyksos--or their descendants in the Delta--grew alarmed lest the native princes might become powerful enough to force them from the throne they had usurped. Determined to check any threatening strength on the part of the Egyptians, the foreigners tried to bring about open conflict, sure themselves of victory. At first the Theban princes sought to avert war, but the demands of the Hyksos grew heavier. There was a folk-story to the effect that the usurping king in the Delta sent word to the Theban prince that the noise of the sacred hippopotami in the pools and canals allowed him rest neither by night or day, and must be disposed of. However simple this appears, it may easily signify that the final break came because of religious difficulties.