As long as Assyria continued to play the role of the subduer of nations, Ashur--the god of war _par excellence_--necessarily retained his position at the head of the Assyrian pantheon.

The popularity of Nabu, which continued to the end of the Assyrian empire, and gained a fresh impetus in the days of Ashurbanabal, who, as a patron of literature, invokes Nabu on thousands of the tablets of his library as 'the opener of ears to understanding,' reacted on his position in the Babylonian cult.

In the new Babylonian empire, which continued to so large a degree the traditions of Assyria, it is no accident that three of the kings--Nabupolassar, Nebuchadnezzar, and Nabonnedos--bear names containing the deity as one of the elements.
While paying superior devotion to Marduk, who once more became the real and not merely the nominal head of the pantheon, they must have held Nabu in no small esteem; and indeed the last-named king was suspected of trying actually to divert the homage of the people away from Marduk to other gods, though he did not, as a matter of course, go so far as to endeavor to usurp for the son, the position held by the father.

It is probably due to Assyrian influence that even in Babylonia, from the eighth century on, Nabu is occasionally mentioned before Marduk.

So Marduk-baladan II.