Charles Ellicott Commentary Isaiah 17:9

"In that day shall their strong cities be as the forsaken places in the wood and on the mountain top, which were forsaken from before the children of Israel; and it shall be a desolation." — Isaiah 17:9 (ASV)

In that day shall his strong cities be as a forsaken bough. —Better, his fortified cities shall be like a forsaken tract of forest and hill-top. These were naturally the usual sites of fortresses (2 Chronicles 27:4), and the gist of the prediction is that they shall be left uninhabited and in ruins. The Septuagint, it may be noticed, either followed a different reading or else gives a curious paraphrase, your cities shall be forsaken, just as the Amorites and Hivites forsook them before the children of Israel. The whole verse reminds us of the great forsaking of Isaiah 6:12.