The sixth angel blew his trumpet. From the four horns of the gold altar that is before God, I heard a voice
References for Revelation 9:13
say to the sixth angel who had the trumpet, "Release the four angels bound at the great river Euphrates."
So the four angels who were prepared for the hour, day, month, and year were released to kill a third of the human race.
The number of mounted troops was 200 million; I heard their number.
References for Revelation 9:16
This is how I saw the horses in my vision: The horsemen had breastplates that were fiery red, hyacinth blue, and sulfur yellow. The heads of the horses were like lions' heads, and from their mouths came fire, smoke, and sulfur.
A third of the human race was killed by these three plagues-by the fire, the smoke, and the sulfur that came from their mouths.
For the power of the horses is in their mouths and in their tails, because their tails, like snakes, have heads, and they inflict injury with them.
The rest of the people, who were not killed by these plagues, did not repent of the works of their hands to stop worshiping demons and idols of gold, silver, bronze, stone, and wood, which are not able to see, hear, or walk.
References for Revelation 9:20
And they did not repent of their murders, their sorceries, their sexual immorality, or their thefts.
References for Revelation 9:21