Why does Nahum speak of the good news of victory if Judah will again be defeated by the Babylonians soon after?

The judgment that the Lord brings on the Assyrians comes in the form of the Babylonian Empire that defeats and wipes out Assyria. Sadly, the historical records show that Judah fails to return to the Lord in faithful worship. They once again turn their backs on him despite him setting them free. The Lord, therefore, uses the Babylonians to once again bring judgment onto Judah. So, the Lord’s promise in Nahum 1:15 that never again shall the worthless pass through you; he is utterly cut off, and his promise in Nahum 1:9 that he will make a complete end to those who plot against him, is referring only to Assyria. The Lord is saying to his people that he will act in this situation. He will remove Assyria forever and never again will Assyria oppress his people. That does not mean that he will never again judge his people if they turn from him, which is exactly what happens with the Babylonian Exile. However, there is also a sense in which Nahum’s words in Nahum 1:9, Nahum 1:15 look forward to a time when the Lord will finally defeat and destroy all of his enemies forever and his people will finally be set free forever. That time comes through Christ whose victory over Satan guarantees the fact that God’s saved people will never again turn away from him.