Adam Clarke on Isaiah 19:23

Shall there be a highway - Under the latter kings of Persia, and under Alexander, Egypt, Judea, and Assyria lived peaceably under the same government, and were on such friendly terms that there was a regular, uninterrupted intercourse between them, so that the Assyrian came into Egypt and the Egyptian into Assyria, and Israel became the third, i.e., was in strict union with the other two; and was a blessing to both, as affording them some knowledge of the true God, Isa 19:24.