Afflicted Judah was the name of Jacob's fourth son and one of the 12 tribes. More will have its affliction reversed.
This verse sets the context for reading the entire book. Nahum does not describe what Judah did to warrant affliction from God. Living in affliction is the context into which hope in the form of the end of Assyrian oppression is announced. Relief from Assyria is central, not triumph over Assyria. The book does not serve imperial aspirations; rather, it promises relief from dominance.