Note again, this has never happened in history past. And it happens when Israel is one people, one nation, and who are back in the land! Assyria is mentioned last, because they simply assist the smaller nations that circle Israel and who invade. Today, Assyria would be Iraq and even maybe Iran, the territory of ancient Assyria.
On these nations God's wrath falls with a tempest. Note that the passage does not mention large Jewish divisions fighting these invading forces. Something spectacular happens that destroys them. God pulverizes them, "makes them like the whirling dust; like chaff before the wind. Like fire that burns the forest, and like a flame that sets the mountains on fire" (vv. 13-14).
The Lord "pursues them with His tempest, and terrifies them with His storm" (v. 15). When their destruction takes place, the enemy will recognize that God is absolutely sovereign, and they "will know that God alone, whose name is the Lord, is the Most High over all the earth" (v. 18).
This chapter does not seem to fit with the seven-year tribulation but with some period before. Unger writes:
It is difficult to fit this confederacy into the prophetic picture of either Russia's future invasion (Ezek. 38-39), but probably before the Tribulation, or that of Antichrist and his invading hordes at Armageddon at the end of the Tribulation (Rev. 16:13-16). Probably its fulfillment will come in some pan-Arabic coalition and attack on the Israeli State before the church is taken out, or at least before Daniel's seventieth week begins.
—Dr. Mal Couch