The Kassites took power after a vacuum was left in Babylonia following the fall of the Amorite kings, whose most successful member was Hammurabi
. The Kassites used a language that they didn't write and so its relationship to other western Asian languages is unknown, although names and some other words in the Kassite language have survived. The Kassites established a capital at Dur-Kurigalzu (modern Aqar-Quf), named for a Kassite king, where they built a ziggurat like the one at Ur, innovating in their building techniques with baked, molded brick. They created a strongly centralized state, with provinces and major cities where administrators loyal to the king were sent. There was a professional military paid in grants of land (as were the administrators), which employed war chariots. The Kassite period of dominance was at the same time as the Mitanni and Assyria in northern Mesopotamia, the Hatti in Anatolia, the New Kingdom in Egypt, and the Middle Elamite Kingdom in western Iran, as is known from Egyptian documents called the Amarna
letters, which detail relationships and etiquette among the area kings. The Kassites sponsored developments in literature and science, including philology. Babylonia was a bilingual culture requiring of its educated members skill in Sumerian and Babylonian.
Sources: Civilizations of Ancient Iraq
, by Benjamin R. Foster and Karen Polinger Foster. Princeton University Press: 2009.
A History of the Ancient Near East, by Marc Can De Mieroop. Blackwell: 2004, 2007.
The Kassites came to power after 16th century Dark Age, however, they had lived in the north of Babylonia from the 18th C. A 1st millennium Babylonia kings list shows Kassite rulers of Babylonia almost 577 years, ending in 1155, when a dynasty from Isin took over.