Whilst Jeremiah and Zephaniah were preaching judgment against Judah, the prophet Nahum was preaching judgment against Nineveh who were one of Judah’s enemies.
The northern kingdom of Israel was already in Assyrian captivity and Assyria itself was still a world dominating power. And so, Nahum preaches a very straightforward message which is, ‘the fall of Nineveh’.
"So do not fear, for I am with you; do not be dismayed, for I am your God. I will strengthen you and help you; I will uphold you with my righteous right hand."