In the late Old Babylonian era, Iraq was conquered by people who came from the east or the northeast, known as the Kassites. They established a new royal family who ruled for five centuries. This era was known as the Middle Babylonian era, which is one of the dark ages in Iraq. The Kassites did not leave us documents or historical records in their original language, but rather they used the language of Babylon. And it seems that they had abandoned their former religion in order to convert to the Babylonian religion. And in the middle of their reign, they established a new capital near present-day Baghdad, which was known as (Dor-Korekalzu), meaning the city of the Kashi king Korikalzo.