The book of Nahum is the prophecy of the coming judgement of the Assyrian’s. While it is primarily written to the people of Ninevah, we can be assured that anyone who stays arrogant & resists God’s authority will face his anger.
The Lord is slow to anger & great in power; the Lord will not leave the guilty unpunished. His way is in the whirlwind & the storm, & clouds are the dust of his feet. The mountains quake before him & the hills melt away. The earth trembles at his presence, the world & all who live in it.
God is slow to be angered. But as the verse says, when he is ready to punish even the earth will tremble & it will come swiftly as a whirlwind.
We sometimes wonder why evil isn't punished immediately & yet, if it was, none of us would be here. God gives us the opportunity to come to him & we can be thankful for the time he gives for people to turn to him.