Many now say that Damascus was never destroyed but have they actually studied the scripture in detail. The translations all seem to miss the exact meaning of the condition coming to Damascus ..."Mutilation"! See the highlighted text below (again from the excellent K&D commentary).
The first turn: “Behold, Damascus must (be taken) away out of the number of the cities, and will be a heap of fallen ruins. The cities of Aroer are forsaken, they are given up to flocks, they lie there without any one scaring them away. And the fortress of Ephraim is abolished, and the kingdom of Damascus; and it happens to those that are left of Aram as to the glory of the sons of Israel, saith Jehovah of hosts.” “Behold,” etc.: hinnēh followed by a participle indicates here, as it does everywhere else, something very near at hand. Damascus is removed מֵעִיר (= עִיר מִהְיוֹת, cf., 1Ki_15:13), i.e., out of the sphere of existence as a city. It becomes מְעִי, a heap of ruins. The word is used intentionally instead of עִי, to sound as much as possible like מֵעִיר: a mutilated city, so to speak. It is just the same with Israel, which has made itself an appendage of Damascus. The “cities of Aroer” (gen. appos. Ges. §114, 3) represent the land to the east of the Jordan: there the judgment upon Israel (executed by Tiglath-pileser) first began. There were two Aroers: an old Amoritish city allotted to the tribe of Reuben, viz., “Aroer on the Arnon” (Deu_2:36; Deu_3:12, etc.); and an old Ammonitish one, allotted to the tribe of Gad, viz., “Aroer before Rabbah” (Rabbath, Ammon, Jos_13:25). The ruins of the former are Arair, on the lofty northern bank of the Mugib; but the situation of the latter has not yet been determined with certainty (see Comm. on Jos_13:25). The “cities of Aroer” are these two Aroers, and the rest of the cities similar to it on the east of the Jordan; just as “the Orions” in Isa_13:10 are Orion and other similar stars. We meet here again with a significant play upon the sound in the expression ‛ârē ‛Aro‛ēr (cities of Aroer): the name of Aroer was ominous, and what its name indicated would happen to the cities in its circuit. עִרְעֵר means “to lay bare,” to pull down (Jer_51:58); and עַרְעָר, עַרִיִרי signifies a stark-naked condition, a state of desolation and solitude. After Isa_17:1 has threatened Damascus in particular, and Isa_17:2 has done the same to Israel, Isa_17:3 comprehends them both. Ephraim loses the fortified cities which once served it as defences, and Damascus loses its rank as a kingdom. Those that are left of Aram, who do not fall in the war, become like the proud citizens of the kingdom of Israel, i.e., they are carried away into captivity. All this was fulfilled under Tiglath-pileser. The accentuation connects אַרָם שְׁאָר (the remnant of Aram) with the first half of the verse; but the meaning remains the same, as the subject to יִהְיוּ is in any case the Aramaeans.