Albert Barnes Commentary Isaiah 37:18

"Of a truth, Jehovah, the kings of Assyria have laid waste all the countries, and their land," — Isaiah 37:18 (ASV)

In truth - It is as he has said: all the nations had been subjected to the arms of the Assyrian. He now intends to add Jerusalem to the number of vanquished cities and kingdoms, and to boast that he has subdued the nation under the protection of Yahweh, as he had done the nations under the protection of idol-gods.

Have laid waste all the nations - The Hebrew, as noted in the margin, is ‘All the lands.’ But this is evidently an elliptical form of expression, meaning all the inhabitants or people of the lands. In (2 Kings 19:17), it is expressed this way: The kings of Assyria have destroyed the nations and their lands.