Wikipedia
The Kassites were a people of the ancient Near East, who controlled Babylonia after the fall of the Old Babylonian Empire c. 1531 BC and until c. 1155 BC ( short chronology). The endonym of the Kassites was probably Galzu, although they have also been referred to by the names Kaššu, Kassi, Kasi or Kashi.
They gained control of Babylonia after the Hittite sack of the city in 1595 BC (i.e. 1531 BC per the short chronology), and established a dynasty based in Dur-Kurigalzu. The Kassites were members of a small military aristocracy but were efficient rulers and not locally unpopular, and their 500-year reign laid an essential groundwork for the development of subsequent Babylonian culture. The horse, which the Kassites worshipped, first came into use in Babylonia at this time.
The Kassite language has not been classified. What is known is that their language was not related to either the Indo-European language group, nor to Semitic or other Afro-Asiatic languages, and is most likely to have been a language isolate (a stand-alone language unrelated to any other), although some linguists have proposed a link to the Hurro-Urartian languages of Asia Minor. However, several Kassite leaders bore Indo-European names, and they might have had an Indo-European elite similar to the Mitanni, who ruled over the Hurro-Urartian-speaking Hurrians of Asia Minor.