Joel, Nahum, and Habakkuk prophesied in the days of Manasseh. But because Manasseh was not righteous, their names were not linked with his (Seder Olam Rabbah 20).
He was righteous. He was also mysterious. Little is known about Nahum except that his book is a vision of the fall of Nineveh.
There is an allusion to the capture of Egyptian Thebes by Ashurbanipal in 663 B.C.E. (Nahum 3:8-10).

Further, there are references to the fall of Assyrian Nineveh to the Babylonians and Medes in 612.
The book seems to have been composed at this precipitate time in the ancient Near East.

Nahum offers a vision - a powerful, eloquent, piercing vision - of the Lord taking revenge against the Assyrians, Israel’s oppressors. The language is vivid and poetic:
She (Nineveh) is empty, and void, and waste;
And the heart melteth, and the knees smite together,
And convulsion is in all loins,
And the faces of them all have gathered blackness (Nahum 2:11).

There is a joyful sense of retaliation that accompanies these three rich prophetic chapters of the Bible. Nahum, perhaps expressing the frustration of his long suffering people, rejoices in Nineveh’s impending destruction:
Woe to the bloody city!
It is all full of lies and rapine;
The prey departeth not.
Hark! the whip, and hark! the rattling of wheels;
And prancing horses, and bounding chariots;
The horseman charging,
And the flashing sword, and the glittering spear;
And a multitude of slain, and a heap of carcasses;
And there is no end of the corpses,
And they stumble upon their corpses (Nahum 3:1-3).

Nahum means “comfort.” What may be derived from this virile rhapsody commemorating the comeuppance of Israel’s rapacious enemy is that the prophet and his people were comforted by the discomfiture of the Assyrian adversary.

Nahum, our artful mysterious poet, defender of Israel.