Who had the first army depends on just what is meant by army. The problem is that small city states existed even before pictographic writing and these city states must surly been able to defend themselves. Sumer is a term used to describe southern Mesopotamia city states established by 3500 BC, but Egypt had both northern and southern city states at this time. All predate known history. In about 3100 BC Egypt was united and this would have taken some type of organized army. Sadly, who had the first army will likely never be known.
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