But the fall of the Dynasty of Ur, like that of the First Dynasty of Babylon, was due to an external cause and not to any movement within the limits of Babylonia itself. We possess no contemporary record of the catastrophe which at this time overwhelmed the empire, but an echo of it has been preserved in an omen-text, inscribed upon an Assyrian tablet from the Library of Ashur-bani-pal. We have already noted instances in which genuine historical traditions have been incorporated in the later augural literature, and we need have no hesitation in accepting the historical accuracy of this reference to past events. The text in question enumerates certain omens which it associates with the fall of "Ibi-Sin, the King of Ur," who, it states, was carried captive to Anshan.[1] We may thus infer that it was an Elamite invasion that put an end to the Dynasty of Ur. The foreign provinces, on the possession of which Dungi had based his claim to the rule of the four quarters of the world, had finally proved the cause of his empire's downfall. We have few data on which to form an estimate of the extent of the Elamite conquest of Babylonia, or of the period during which the country or a portion of it was in the hands of the invaders. The deportation of the king of Ur can hardly have been the result of a spasmodic raid, following one of the numerous provincial revolts which had at last proved successful. It is far more likely that the capture followed the fall of Ur itself, and such an achievement argues the existence of an organized force in Elam, which it must have required some years to build up. It is therefore permissible to conjecture that, in the course of the twenty-five years of his reign, Ibi-Sin had gradually been losing his hold upon the Elamite portion of his empire, and that an independent kingdom had been formed in Elam under a native ruler. For a time Ibi-Sin may have continued to hold certain districts, but, after the successful invasion of Babylonia, the whole of Elam, and for a time a part of Babylonia itself, may have fallen to the lot of the conqueror.