Matthew Henry on Nahum 3:8-19

Strong-holds, even the strongest, are no defence against the judgments of God. They shall be unable to do any thing for themselves. The Chaldeans and Medes would devour the land like canker-worms. The Assyrians also would be eaten up by their own numerous hired troops, which seem to be meant by the word rendered “merchants.” Those that have done evil to their neighbours, will find it come home to them. Nineveh, and many other cities, states, and empires, have been ruined, and should be a warning to us. Are we better, except as there are some true Christians amongst us, who are a greater security, and a stronger defence, than all the advantages of situation or strength? When the Lord shows himself against a people, every thing they trust in must fail, or prove a disadvantage; but he continues good to Israel. He is a strong-hold for every believer in time of trouble, that cannot be stormed or taken; and he knoweth those that trust in Him.