In the middle of the third millennium, the floodplains of the Tigris and Euphrates rivers were home to a cluster of city-states, which collectively comprised the Sumerian civilization. The Treaty of Mesilim, inscribed in cuneiform on a stele, or stone pillar, is the world’s oldest known legal agreement. It refers to a boundary dispute between Umma and Lagash, two adjacent states on the banks of the Tigris, near the Persian Gulf. The stele refers to Umma’s trespass across a border set by Mesilim, an earlier king, and proclaims that the boundary, running along an irrigation canal, should be confirmed by boundary stones. The dispute would continue to fester, and about 200 years later, the Umma king invaded Lagash and destroyed its capital, Girsu. His triumph was short lived. The Akkadian warlord, Sargon the Great, conquered all the Sumerian cities a few years later, paying scant attention to boundary stones.
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