The oracles against Ethiopia and Egypt in Isaiah 18-20 are more of the same kinds of prophecy as other proclamations against nations around Judah. The author of these passages predicts that Ethiopians will bring gifts to Yahweh's temple in Jerusalem, and that Egyptians will be plagued with infighting, drought, and eventually a harsh king. Later, the author claims, Egypt will experience mercy from the Israelites' supernatural, and several cities will be dedicated to Yahweh. Egypt and Assyria will be alongside Judah, reconciled and claimed as Yahweh's chosen people. The short passage that follows depicts Isaiah's sign-act of walking around naked for three years, interpreting that act to symbolize the captivity of Ethiopia and Egypt.
Scholars have a difficult time with these oracles, because there is no apparent place in known history that can match up with the implied events of the prophecies. Some aspects and details may seem to have relevance, but then other details would be out of place. This limits the application of the text as a historical testament of events or as an accurate forecasting of events that were yet to happen when the oracles were written. Since it's obvious that some editorial work has been done to create the existing versions of the book of Isaiah, some scholars attempt to rearrange passages to get a more accurate or sensible account. None of this work has any bearing on whether one can find meaning in the passage for life in the twenty-first century. If passages like this are about historical events, then their usefulness is exclusively past tense, since the events they describe either happened or failed to happen centuries ago. If one insists that the predictions are simply to demonstrate the power and authority of the Israelite deity, one must take into consideration that it's not clear that all of what is predicted here ever came to pass. In addition, a reader who already has a theistic bias doesn't need a passage about ancient nations to serve as evidence for God's power and authority, and a reader who doesn't have a theistic bias won't be convinced by the vague (and in some cases inaccurate) predictions of this passage.
A we've seen before, there are some problems with assuming that God is responsible for military conquests and natural disasters. Although the authors of Isaiah and other prophets had their reasons for seeing their supernatural as head over all nations' war efforts, they didn't understand the ramifications of their claims. They saw their society as unjust, with the wealthy and powerful neglecting their responsibilities toward the poor and disenfranchised. They saw their society as immoral, offering disingenuous religious sacrifices while they maintained systems of greed and self-indulgence. A foreign army at their doorstep was a clear indication to these prophets that Yahweh was unhappy, and that he was going to use whatever means were at his disposal to effect the curses for disobedience proclaimed in the Sinai covenant. These same prophets trusted that Yahweh would also gladly bless the Israelites, if the people fulfilled the supernatural's expectations.
One cannot maintain a view of a god worth worshiping and also insist that such a deity was at the head of every military and ordaining the decisions of every government. It was fine motivation for change that the Israelites saw Yahweh behind their exiles, because in doing so they understood something about how their society had failed its own people. They also had the luxury of seeing their god behind their return from exile. In our time, we would have to see God as the one who ordained the many genocidal acts of the twentieth century, some of which continue in parts of the world today. We would have to see God as the true commander who ordered atomic bombs to be inflicted upon thousands of non-combatants in Japan. If God is the kind of deity depicted in Isaiah and other prophets of Hebrew scripture, all atrocities of war can be justified by a simple acknowledgment that the people who suffered or died did not live up to the demands placed on them by a supernatural.
The authors of Isaiah weren't necessarily off-base regarding what they wanted for their society, and even for their neighboring societies. This passage on Egypt has some pretty favorable predictions for what Yahweh will eventually do for that nation. The view of society's potential presented in Isaiah places justice, equity, and compassion high on the list of desirable qualities, and it sees these qualities as attainable by a people, particularly the people in charge. The authors may have been displaying a perspective that their supernatural was superior to every other nation's, but they were equally critical of their own people for failing to live by the standards that supernatural had set for them.
Israelite understanding of their agreement with Yahweh was not unlike other treaties between unequal powers in the Ancient Near East. The more powerful entity essentially tells the less powerful entity, "This is what you're going to do, and this is what I'm going to do." Basically, if the less powerful nation does everything that that the powerful ruler demands, then they get the benefits of the arrangement. However, if the less powerful nation fails to do everything the powerful ruler demands, then the curses of the treaty were valid responses by the ruler. There were perhaps phrased in colorful and symbolic terms, but essentially the ruler would take military action against the disobedient weaker subjects. That's how Israel and Judah saw their relationship with Yahweh. The supernatural said, "Here are my demands. Meet them and live prosperously; fail to meet them and die."
Through all of this proclamation of doom though, there is an undercurrent of hope. Isaiah 19 forecasts a future in which peaceful relations and unity exist between nations, at least between Egypt, Assyria, and Judah. This is a bit humorous, considering Judah's insignificance as a political power. Egypt was the seat of the previous empire, and Assyria was the seat of the current empire. Perhaps the prophet was hopeful that Judah would be the seat of a future empire; such a vision of the future is certainly suggested by other passages in Isaiah. Of course, that never happened, and it isn't likely to happen. The basic gist of that future alliance, though, was that justice and peace would be the rule rather than the exception. The vision of an empire ruled by Yahweh was that it would be the sort of place any person would want to live: where no one would go hungry, and no one would be afraid (Micah 4:4).
The values are a bit inspiring. The way the authors of Isaiah thought it would happen is a bit disappointing. They didn't think that people were actually capable of creating such a reality. They asserted that their god would make it so. Perhaps one could say that, just as Yahweh was seen as the primary actor when a foreign army swept in, Yahweh can also be seen as the primary actor when people make decisions that lead toward peace and justice. The tendency, however, is for people to abdicate responsibility for creating peace and justice. If we do not place the responsibility on a supernatural, perhaps we place responsibility on the government to make the kind of world we most want to live in. We may laugh at the suggestion, but that doesn't change our expectations.
There is, of course, another way of seeing the covenant promises and curses without assuming the existence of a supernatural. However the ancients thought of their world and society, they understood intuitively what characteristics and practices helped a society thrive and what characteristics and practices tore a society down. That their supernatural does not exist has no bearing on the value of justice, equity, and compassion. The view toward a world in which people are safe and have enough is still an inspiring vision. Human beings have to take responsibility for their actions in order for our reality to approach that vision.
God is not at the head of the military; human beings are. God is not in control of who has wealth and power; human beings are. God doesn't commit war atrocities; human beings do. God doesn't effect genocide; human beings do. God cannot respond compassionately to the world; human beings can. God is not capable of creating justice and equity; human beings must.
Whatever our vision of the world is, we are responsible for moving toward that, even if our only sphere of influence is our own lives. When we set aside fear, I suspect that most of us want the same kind of world, and I suspect that we value the same sorts of things that the prophets valued: justice, equity, and compassion. Aside from irrational fear, why wouldn't we all want to live in a sustainable world where no one went hungry and no one was oppressed? If that is our most noble vision for the planet, that is what we are called to create. We aren't called by some supernatural outside of ourselves; we call ourselves by the values we hold. When you set aside fear, what is your vision for the world? What will you do today to bring your life a little bit closer to that vision?