Wikipedia
Ibbi-Sin, son of Shu-Sin, was king of Sumer and Akkad and last king of the Ur III dynasty, and reigned c. 1963 BC-1940 BC ( Short chronology). During his reign, the Sumerian empire was attacked repeatedly by Amorites. As faith in Ibbi-Sin's leadership failed, Elam declared its independence and began to raid as well.
Ibbi-Sin ordered fortifications built at the important cities of Ur and Nippur, but these efforts were not enough to stop the raids or keep the empire unified. Cities throughout Ibbi-Sin's empire fell away from a king who could not protect them, notably Isin under the Amorite ruler Ishbi-Erra. Ibbi-Sin was, by the end of his kingship, left with only the city of Ur. In 1940 BC, the Elamites, along with "tribesmen" from the region of Shimashki in the Zagros Mountains" (Stiebing 79) sacked Ur and took Ibbi-Sin captive; he was taken to the city of Elam where he was imprisoned and, at an unknown date, died.