This desolation, at God’s hand, will take place at the end of the Great Tribulation “in the days of the voice of the seventh angel, when he shall begin to sound” (Rev 10:7)
The prophecies pertaining to God’s “two witnesses” will be fulfilled just prior to the last trump:
Egypt was warned:
"And Lot lifted up his eyes, and beheld all the plain of Jordan, that it was well watered every where, before the LORD destroyed Sodom and Gomorrah, even as the garden of the LORD, like the land of Egypt, as thou comest unto Zoar. (Gen 13:10)"