The earliest mention of them is found in the tablets which were compiled for the library of Sargon I. of Accad, in which reference is made to the Khatti, which probably means Hittites, showing that at this remote period, about 3800 B.C., they had already moved down from their northern home into the valley of the Euphrates and Upper Syria. Their affinity with the Accadians of Chaldæa is clearly proved by their language, which the recent discovery of papyri at Tell-el-Amara, containing despatches from the tributary King of the Hittites to Amenophus IV., written in cuneiform characters, has proved to be almost identical with Accadian. It seems probable that part of the army which fought in defence of Troy may have been Hittite, and there are many indications that the Etruscans, who were generally believed to have come from Lydia, were of the same race and spoke the same language. It is in Egyptian records, however, that we meet with the first definite historical data respecting this ancient Hittite Empire. In these they are referred to as "Kheta," and probably formed part of the great Hyksos invasion; but the first certain mention of them occurs in the reign of Thotmes I., about 1600 B.C., and they appear as a leading nation in the time of Thotmes III., who defeated a combined army of Canaanites and Hittites under the Hittite King of Kadesh, at Megiddo, and in fourteen victorious campaigns carried the Egyptian arms to the Euphrates and Tigris. For several subsequent reigns we find the Hittites enumerated as one of the nations paying tribute to Egypt, whose extensive Empire then reckoned Mesopotamia, Assyria, Phoenicia, Palestine, Cyprus, and the Soudan among its tributary states. Gradually the power of Egypt declined, and in the troubled times which followed the attempt of the heretic King Ku-en-Aten to supersede the old religion of Egypt by the worship of the solar disc, the conquered nations threw off the yoke, and the frontiers of Egypt receded to the old limits. As Egypt declined, the power of the Hittites evidently increased, for when we next meet with them it is contending on equal terms in Palestine with the revival of the military power of Egypt under Ramses I., the founder of the nineteenth dynasty, and his son Seti I.