Denotes inroads of enemies, killing, and destruction, Rev. 8:7. Rev. 11:19, Rev. 16:21. All of which denotes a destructive force sent by God, Isa. 10:5. Assyria will be punished in battles, Isa. 28:2, 17; 30:30-33; Hag. 2:17.
[For a more in-depth study on biblical symbolism see eschatology “Study Series 5b Hebraic Language Symbolism”]