And upon every lofty tower What he adds about towers and walls is not figurative or metaphorical. We know how men, when they think that they are well defended, congratulate themselves that they no longer need the assistance of God. Accordingly, under the name of towers and walls Isaiah mentions the object of false confidence; for if any place seem to be impregnable, there do irreligious men build their nest, that they may look down from it on heaven and earth; for they imagine that they are placed beyond all the uncertainties of fortune. Isaiah therefore threatens that, when it shall please God to humble men, he will throw down all the defenses on which they place a false confidence. And although those things are not in themselves evil, yet because they receive too large a share of our attention, it is with great propriety that Isaiah sharpens his pen against them. To the same purpose is what he says about horses and chariots; for, as we are told by Micah, because men have improperly relied on earthly riches, they must be altogether deprived of them, that they may owe this preservation entirely to the hand of God. (Micah 5:10.) A little before, he had reproved them for the abundance of their horses (verse 7); he now addresses them about the judgment of God, and warns them that, as the only possible way of gaining the favor of God, he must take from the Jews all their horsemen, that they may no longer place sinful reliance on earthly support.

Every high tower - Towers, or fortresses, were erected for defense and protection. They were made on the walls of cities, for places of observation (compare the note at Isaiah 21:5), or in places of strength, to be a refuge for an army, and to be a point from which they might sally out to attack their enemies. They were "high" to afford a defense against being scaled by an enemy, and also that from the top they might look abroad for observation; and also to annoy an enemy from the top, when the foe approached the walls of a city.
Every fenced wall - הומה בצוּרה betsûrâh hômâh. The word "fenced," בצוּרה betsûrâh, is from בצר bâtsar, to make inaccessible, and hence, to fortify. It denotes a wall that is inaccessible, or strongly fortified. Cities were commonly surrounded by high and strong walls to defend them from enemies. The sense is, God would overturn all their strong places of refuge and defense.

And upon every high tower, and upon every fenced wall. Which may signify everything that serves to support and defend the antichristian hierarchy, particularly the secular powers. The Targum paraphrases it,
"and upon all that dwell in a high tower, and upon all that reside by a fortified wall.''

tower . . . wall--Towers were often made on the walls of cities.
fenced--strongly fortified.

The glory of nature is followed by what is lofty and glorious in the world of men, such as magnificent fortifications, grand commercial buildings, and treasures which minister to the lust of the eye. "As upon every high tower, so upon every fortified wall. As upon all ships of Tarshish, so upon all works of curiosity." It was by erecting fortifications for offence and defence, both lofty and steep (bâzur, praeruptus, from bâzar, abrumpere, secernere), that Uzziah and Jotham especially endeavoured to serve Jerusalem and the land at large. The chronicler relates, with reference to Uzziah, in 2 Chron 26, that he built strong towers above "the corner-gate, the valley-gate, and the southern point of the cheesemakers' hollow," and fortified these places, which had probably been till that time the weakest points in Jerusalem; also that he built towers in the desert (probably in the desert between Beersheba and Gaza, to increase the safety of the land, and the numerous flocks which were pastured in the shephelah, i.e., the western portion of southern Palestine). With regard to Jotham, it is related in both the book of Kings (2-Kings 15:32.) and the Chronicles, that he built the upper gate of the temple; and in the Chronicles (2-Chronicles 27:1-9) that he fortified the 'Ofel, i.e., the southern spur of the temple hill, still more strongly, and built cities on the mountains of Judah, and erected castles and towers in the forests (to watch for hostile attacks and ward them off). Hezekiah also distinguished himself by building enterprises of this kind (2-Chronicles 32:27-30). But the allusion to the ships of Tarshish takes us to the times of Uzziah and Jotham, and not to those of Hezekiah (as Psalm 48:7 does to the time of Jehoshaphat); for the seaport town of Elath, which was recovered by Uzziah, was lost again to the kingdom of Judah during the reign of Ahaz. Jewish ships sailed from this Elath (Ailath) through the Red Sea and round the coast of Africa to the harbour of Tartessus, the ancient Phoenician emporium of the maritime region watered by the Baetis (Guadalquivir), which abounded in silver, and then returned through the Pillars of Hercules (the Straits of Gibraltar: vid., Duncker, Gesch. i. 312-315). It was to these Tartessus vessels that the expression "ships of Tarshish" primarily referred, though it was afterwards probably applied to mercantile ships in general. The following expression, "works of curiosity" (sechiyyoth hachemdah), is taken in far too restricted a sense by those who limit it, as the lxx have done, to the ships already spoken of, or understand it, as Gesenius does, as referring to beautiful flags. Jerome's rendering is correct: "et super omne quod visu pulcrum est" (and upon everything beautiful to look at); seciyyâh, from sâcâh, to look, is sight generally. The reference therefore is to all kinds of works of art, whether in sculpture or paintings (mascith is used of both), which delighted the observer by their imposing, tasteful appearance. Possibly, however, there is a more especial reference to curiosities of art and nature, which were brought by the trading vessels from foreign lands.

Wall - To which you trusted for your defence.