Matthew Poole and continuators on Jeremiah 46:23

23 They shall cut down her forest, saith the LORD, though it cannot be searched , because they are more then the grashoppers, and are innumerable .

Egypt is compared to a forest either for the multitude of Cities, or of people in that Countrey, and to a thick Forest, because as it is an hard thing to make ones way through a Forest, so it was judged as hard for an Enemy to make his way into that Country, in humane probability Egypt could not be searched, yet (saith God) the Caldeans shall cut down this Forest, and it shall be no more to them then for hewers of Wood, with Tools fitted for the purpose, to make their way through a forest.

For the Army of the Caldeans shall be as numerous as the inhabitants of Egypt, more then the Grashoppers which come in such Troops, as in a short time they devour every green Herb in a place.