What will trigger the Jews to flee to the mountains southwest of Jerusalem?
The tribulation described in Matthew 24:21, when Satan's wrath and God's wrath are poured out on the human race, will trigger the Jewish remnant to flee from Jerusalem to the mountains southwest, where God will protect them for three and a half years.
Les explains that another triggering mechanism will cause these Jews to go down to the mountains southwest of Jerusalem. He calls this the Escaping Remnant—not the whole nation, but a remnant from every category of life. They will flee the area of Jerusalem to the mountains, possibly to Petra, though he does not know. Their God will watch over and protect them for the entire three and a half years. The tribulation as normally thought begins here; the whole seven years is tribulation, and the last three and a half years will be especially severe when Satan's wrath and God's wrath are poured out, as Matthew 24:21 describes.