Revelation 9:14

Release the four angels. These are evil angels. Note they have been bound at the great river. [The four angels of Revelation 7:1 are good angels, who "stand at the four corners of the earth."] As these evil angels are released, the same powers of evil that do the work of destruction in the hearts and lives of men, change these wicked men into devils (so to speak). In times of war, wicked people lose the thin veneer of morality and civilization [the atrocities of any war show this]. The sixth Trumpet paints a picture of war; not one specific war, but ALL WAR - past, present, and future. The four evil angels are pleased with the idea of plunging all mankind into war. Yet they cannot act unless God permits [they were bound]! Let us keep in mind, that in allowing them to be released, God uses even war as a voice calling for the wicked to repent (compare Revelation 9:20-21). [The Trumpets of Revelation 9 answer the question: "How can a loving God allow pain and suffering?" To the Christian who suffers in pain, this is a Seal (compare Revelation 7:2-3 note); but to the unbeliever, this pain and suffering is a Trumpet of warning!] The great river Euphrates. This symbolizes Assyria and Babylon, therefore, the entire wicked world.