Oracle about Cush.
People agree this is about Ethiopia. It was at that time the major regional power in Africa along with Egypt. The battle for dominance of the middle East was lining up to be between two heavy weights, Assyria vs Egypt for all the other land, and in that battle Israel may have had the offer to join an alliance with the two nations.
All of which might explain the reference to “ambassadors by sea” at the start.
The chapter seems to then talk about reverse ambassadors. There is no judgement of Cush mentioned here, is more like it tells them to look and listen to what happens to Israel, to learn about God’s might, and that the example of Israel will be a message to all nations.
Cush will eventually bring tribute to Israel. Some suggest that the Queen of Sheba may have been a queen of Ethiopia. Which means there may have already been a tradition of respect for Israel.
It’s a fairly obscure prophesy, but in the near sense it seems to be about the judgement of Israel being inevitable, and local politicking making no difference.
In the far meaning, it seems to be about Ethiopia becoming a centre for the church in Africa, which it did. It is certainly a useful passage to look at when ideology comes up about racial inferiority. God judges his own people to bless Africa.
We are all equal before God, and all have access to grace.