Nebuchadnezzar of the Old Testament was a ruler of Babylon.

Babylon had kings. In the related links I posted the information.

Belshazza and Nebuchadnezzar became kings of Babylon

There is a wide numbers in the Babylon dynasty. From Sargon to Nebuchadnezzar II there was a long list of kings but after the last babylon king died the median king entered the city and became part of the median Empire and after time the Persians entered. There were no war at the change of powers since one king died who married to other kings so the next in the families got the throne.

Daniels history is a great one. Kings made him an adviser.