John Gill Commentary Ezekiel 32:15

"When I shall make the land of Egypt desolate and waste, a land destitute of that whereof it was full, when I shall smite all them that dwell therein, then shall they know that I am Jehovah." — Ezekiel 32:15 (ASV)

When I shall make the land of Egypt desolate: The cities being demolished, the inhabitants destroyed with the sword, or carried captive. And the country shall be destitute of that whereof it was full: men and cattle, corn and other fruits of the earth, wealth and riches, pomp and grandeur. When I shall smite all them that dwell therein: with the sword of the Chaldeans.

Then shall they know that I am the Lord. For God is known in the perfections of his nature, omnipotence, omniscience, holiness, justice, &c. by the judgments he executes; for this is not to be understood of a spiritual knowledge of him, but of a terrible conviction of the truth of his being and attributes, by the awful dispensations of his providence.