What made it harder to live in sumer than in the zagros foothills?

The aspect which made it harder to live in Sumer than in the Zagros foothills was that, Sumer lacked natural barriers such as hills, mountain ranges, or different land forms or water forms around it to keep out enemies from Sumer territory. The Sumer territory was found near the Rivers Tigris and Euphrates, though it is found between two rivers, this territory has been conquered by a different civilization/empire

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