The oldest kingdom that was ruled by central king was Akkadian Empire. Before Akkadian Empire, the kingdoms were ruled by landlords.
Salgon I was the first emperor of the world history. He managed to unite all Akkadian tribes and established the first central kingdom. Although he was an Akkadian leader, his empire was extended to Small Asia. He left deep traces in history. Salgon I was having the title “world dominant” and he wasthe first. He saved Akkadians from slavery and he established his empire.
The Akkadian Empire had a huge dominant zone. We can come across the impact of empires after them.