“Prepare for war!” In Joel 3:9-11 the nations, who have been so quick to fight and conquer Israel, are now challenged to fight with God. The nations are told to “Stir up the mighty men” (v. 9); “Beat your plowblades into swords, and your pruning hooks into spears” (v. 10); and call even the weak man strong (v. 10). Then all the nations around Israel are called to gather together to fight with God (v. 11). But the last sentence of Joel 3:11 changes and addresses God, not the enemy nations. “Cause your mighty ones to come down there, O Yahweh.” So in Joel 3:9-11 the nations are summoned together to fight with God.
However, the last sentence of Joel 3:11 is a complete change. Someone, likely the prophet although the speaker is not identified, requests that God send down His “mighty ones” (or “strong ones,” “warriors,” “heroes”) to fight this army of unbelievers. This is clearly a foreshadowing of the Battle of Armageddon when God’s heavenly army will come down from heaven and fight and destroy the army on earth that Satan has gathered (Rev. 16:12-16; 19:11-21). This idea is reinforced by the fact that after the battle in Joel 3:11, the Judgment is portrayed in the next verse, Joel 3:12.