Assyrian monarchy
The Assyrian monarchy was characterized by the fact that it was hereditary. The king would choose his crown prince during his lifetime from among his children, and impose allegiance and loyalty to him on the princes, notables, and senior army commanders.
It is customary for the Crown Prince to leave the palace of his father, the King, to live in his own palace, where he is prepared for the duties of government, as he is taught the functions and duties of kingship and methods of governance, and is entrusted with important military and administrative tasks, including acting on behalf of his father, the King, during his absence.
Some of the crown princes received high training and education, especially mentioning here King Ashurbanipal, who said:
I studied the wisdom of the god Nabu and mastered the art of copying clay tablets. I was able to solve complex problems in division and multiplication. I mastered the extremely difficult art of Sumerian and Akkadian writing. I worked hard to learn royal etiquette and behavior, so I would appear in the presence of my father to issue orders to the nobles and princes.
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Source: History of Art in Mesopotamia/babylon tbe gate if gods-Zuhair Sahib/ Part Three