And the fortress. The Prophet now directs his discourse to the country of Moab. It was highly fortified, and was proud of its walls and fortifications; and he affirms that the lofty towers, and other defences, however strong and seemingly impregnable, will be of no avail. The ancients, it is well known, had quite a different method of fortifying from what is practiced among us. He will bring down, lay low, and cast to the ground. The three words here employed, for conveying the meaning more strongly, are not superfluous; for it was necessary to beat down that pride which swelled the hearts of the Moabites, and which, as we formerly saw, [1] made them intolerable. The Prophet therefore mocks at them, "As if the Lord could not cast down that loftiness of which you boast!" To the dust. The meaning of this clause is as if he had said, "He will not only level it with the ground, but will reduce it to dust, so that there will not even be a trace of the ancient ruin." This passage contains an excellent and highly seasonable consolation; for the enemies of the Church in the present day are so haughty, that they mock not only at men, but at God himself, and are so much swelled and puffed up by their power, that they imagine themselves to be invincible; but, in opposition to their bulwarks and defences, we ought to bring forward this declaration of the Prophet, "The Lord will quickly bring down and lay them low." Yet we must patiently endure to see them strong and powerful, till the full time for their destruction arrive.

Footnotes

1 - See Commentary on Isaiah, [20]vol. 1 p. 488

And the fortress - Thy strong defenses shall be destroyed. This is spoken of Moab (compare the notes at Isaiah 15:1-9;Isaiah 16:1-14), and is designed to be emblematic of the enemies of the people of God (compare the notes at Isaiah. 34) The repetition of the expressions 'bring down,' 'lay low,' and 'bring to the ground,' is designed to make the sentence emphatic, and to indicate that it would certainly be accomplished.

And the fortress of the high fort of thy walls shall he bring down,.... That is, their high and, fenced walls, which were about their cities, the fortifications of them; these should be destroyed by the Lord, be battered and brought down, not being able to stand against his mighty power. The Targum renders it,
"the mighty city, the cities of the nations;''
and may design the city of Rome, and the cities of the nations that shall fall at the pouring out of the seventh and last vial, Revelation 16:19 it follows,
lay low, and bring to the ground, even to the dust; which variety of words without any copulative are used to express the sudden, quick, certain, and irrecoverable destruction of such fortified city, or cities, and their fortifications.

fortress--the strongholds of Moab, the representative of the foes of God's people [BARNES]. Babylon [MAURER]. The society of infidels represented as a city (Revelation 11:8).
As the overthrow of the apostate faction is described in the twenty-fifth chapter, so the peace of the faithful is here described under the image of a well-fortified city.

And - All thy fortifications, in which thou trustest.