It was from one of these Elamite monarchs that Sin-muballit captured Isin, and probably the Elamites were also the leaders of the army of Ur which he had routed before that event took place. He was not successful, however, in driving the Elamites from the land, and possibly he arranged with them a treaty of peace or perhaps of alliance. Much controversy has been waged over the historical problems connected with this disturbed age. The records are exceedingly scanty, because the kings were not in the habit of commemorating battles which proved disastrous to them, and their fragmentary references to successes are not sufficient to indicate what permanent results accrued from their various campaigns. All we know for certain is that for a considerable period, extending perhaps over a century, a tremendous and disastrous struggle was waged at intervals, which desolated middle Babylonia. At least five great cities were destroyed by fire, as is testified by the evidence accumulated by excavators. These were Lagash, Umma, Shurruppak, Kisurra, and Adab. The ancient metropolis of Lagash, whose glory had been revived by Gudea and his kinsmen, fell soon after the rise of Larsa, and lay in ruins until the second century B.C., when, during the Seleucid Period, it was again occupied for a time. From its mound at Tello, and the buried ruins of the other cities, most of the relics of ancient Sumerian civilization have been recovered. It was probably during one of the intervals of this stormy period that the rival kings in Babylonia joined forces against a common enemy and invaded the Western Land. Probably there was much unrest there. Great ethnic disturbances were in progress which were changing the political complexion of Western Asia. In addition to the outpourings of Arabian peoples into Palestine and Syria, which propelled other tribes to invade Mesopotamia, northern Babylonia, and Assyria, there was also much unrest all over the wide area to north and west of Elam. Indeed, the Elamite migration into southern Babylonia may not have been unconnected with the southward drift of roving bands from Media and the Iranian plateau. It is believed that these migrations were primarily due to changing climatic conditions, a prolonged "Dry Cycle" having caused a shortage of herbage, with the result that pastoral peoples were compelled to go farther and farther afield in quest of "fresh woods and pastures new". Innumerable currents and cross currents were set in motion once these race movements swept towards settled districts either to flood them with human waves, or surround them like islands in the midst of tempest-lashed seas, fretting the frontiers with restless fury, and ever groping for an inlet through which to flow with irresistible force.