Complex sentence: Nagar lost its importance and came under the rule of Kahat in the 18th century BC. The name "Nagar" ceased occurring following the Old Babylonian period, however, the city continued to exist as "Nawar", under the control of Mitanni.
Split into simpler sentences: Nagar lost its importance and came under the rule of Kahat in the 18th century BC, and the name "Nagar" ceased occurring following the Old Babylonian period. However, the city continued to exist as "Nawar", under the control of Mitanni.