So there you are, an ancient Assyrian, and Yahweh uses you as a holy weapon of judgment on his disobedient people. You do your job, sack their homes, carry them off to who knows where, and what does all that get you?
The prophet Nahum getting in your face about how God is going to layeth the smacketh down on you for a job well done.
While other Minor Prophets temper their tempers with a side order of mercy, Nahum is having none of that. Assyria’s number-one city, Nineveh, is responsible for making the lives of God’s people miserable, and even if the Israelites deserved it, the Ninevites are going to get what they deserve.
If by “deserved” you mean “wiped out because they implement God’s fateful decree.” Y’see, according to Nahum, the fact that Yahweh calls the shots means bupkis when it comes to punishing people for doing something bad.
A jealous and avenging God is the Lord, the Lord is avenging and wrathful; the Lord takes vengeance on his adversaries and rages against his enemies. (NRSV 1:2)
See, I am against you, says the Lord of hosts, and I will burn your chariots in smoke, and the sword shall devour your young lions; I will cut off your prey from the earth, and the voice of your messengers shall be heard no more. (NRSV 2:13)
I am against you, says the Lord of hosts, and will lift up your skirts over your face; and I will let nations look on your nakedness and kingdoms on your shame. I will throw filth at you and treat you with contempt, and make you a spectacle. Then all who see you will shrink from you and say, “Nineveh is devastated; who will bemoan her? Where shall I seek comforters for you?” (NRSV 3:5-7)
There’s no pleasing some people. Or gods.