The Sumerian city-states were not united as one entity; instead, they all were their own independent states (Yoffee). This allowed violent conflicts to occur between the city-states because they had no central authority in place to prevent war. If we put this idea into modern times, it would be like Pennsylvania and Delaware going to war over who owned rights to the Delaware River which separates the two states. However, since Pennsylvania and Delaware are united under one authority, this conflict would not happen, and if it did, then there would be a larger power to end the dispute. One of the most noted disputes with the Sumerian city-states is the conflict between the city-states Umma and Lagash.