The people of Egypt and Cush would be carried off by the king of Assyria. It is made clear that the exiled people would be made to walk naked and barefoot, just like Isaiah did. Captives were often carried away naked and barefoot, not only because it was demoralizing, but also because it made escape less likely.
The word lead
in the first part of the verse indicates that, just as sheep are entirely at the mercy of their shepherd, so captives are utterly subject to their captor. The last part of the verse indicates their total disgrace.
4 so shall the king of Assyria lead away the Egyptian captives and the Cushite exiles, both the young and the old, naked and barefoot, with buttocks uncovered, the nakedness of Egypt.