A long period of darkness separates the Middle and Neo-Elamite periods. In 742 BC a certain Huban-nugash is mentioned as king in Elam. The land appears to have been divided into separate principalities, with the central power fairly weak. The next 100 years witnessed the constant attempts of the Elamites to interfere in Mesopotamian affairs, usually in alliance with Babylon, against the constant pressure of Neo-Assyrian expansion. At times they were successful with this policy, both militarily and diplomatically, but on the whole, they were forced to give way to increasing Assyrian power. Local Elamite dynastic troubles were from time to time compounded by both Assyrian and Babylonian interference. Meanwhile, the Assyrian army whittled away at Elamite power and influence in Luristan. In time these internal and external pressures resulted in the near-total collapse of any meaningful central authority in Elam. In a series of campaigns between 692 and 639 BC, in an effort to clean up a political and diplomatic mess that had become a chronic headache for the Assyrians, Ashurbanipal’s armies utterly destroyed Susa, pulling down buildings, looting, and sowing the land of Elam with salt.
Note: The information on this page was found at Britannica.com