The conquest of Kazallu, winch Sumu-abum carried out in the last year but one of his reign, was the most important of Babylon's early victories, for it marked an extension of her influence beyond the limits of Akkad. The city appears to have lain to the east of the Tigris, and the two most powerful empires in the past history of Babylonia had each come into active conflict with it during the early years of their existence. Its conquest by Akkad was regarded in Babylonian tradition as the most notable achievement of Sargon's reign; and at a later period Dungi of Ur, after capturing the Elamite border city of Dêr, had extended his empire to the north or east by including Kazallu within its borders.[57] Sumu-abum's conquest was probably little more than a successful raid, for in the reign of Sumu-la-ilum Kazallu in its turn attacked Babylon, and, by fully occupying her energies, delayed her southward expansion for some years. In the earlier part of his reign Sumu-la-ilum appears to have devoted himself to consolidating the position his predecessor had secured and to improving the internal resources of his kingdom. The Shamash-khegallum Canal, which he cut immediately on his accession, lay probably in the neighbourhood of Sippar; and later on he further improved the country's system of irrigation by a second canal to which he gave his own name.[58] The policy he thus inaugurated was energetically maintained by his successors, and much of Babylon's wealth and prosperity under her early kings may be traced to the care they lavished on increasing the area of land under cultivation. Sumu-la-ilum also rebuilt the great fortification-wall of his capital, but during his first twelve years he records only one military expedition.[59] It was in his thirteenth year that the revolt and reconquest of Kish put an end to this period of peaceful development. The importance attached by Babylon to the suppression of this revolt is attested by the fact that for five years it formed an era for the dating of documents, which was only discontinued when the city of Kazallu, under the leadership of Iakhzir-ilum, administered a fresh shock to the growing kingdom by an invasion of Babylonian territory. Iakhzir-ilum appears to have secured the co-operation of Kish by inciting it once more to rebellion, for in the following year Babylon destroyed the wall of Anu in that city; and, after re-establishing her authority there, she devoted her next campaign to carrying the war into the enemy's country. That the subsequent conquest of Kazallu and the defeat of its army failed to afford a fresh subject for a nascent era in the chronology is to be explained by the incompleteness of the victory; for Iakhzir-ilum escaped the fate which overtook his city, and it was only after five years of continued resistance that he was finally defeated and slain.[60]