The sixth angel sounded his trumpet, and I heard a voice coming from the four horns of the golden altar that is before God. 14 It said to the sixth angel who had the trumpet, “Release the four angelswho are bound at the great river Euphrates.” 15 And the four angels who had been kept ready for this very hour and day and month and year were released to kill a third of mankind. 16 The number of the mounted troops was twice ten thousand times ten thousand. I heard their number.
17 The horses and riders I saw in my vision looked like this: Their breastplates were fiery red, dark blue, and yellow as sulfur. The heads of the horses resembled the heads of lions, and out of their mouths came fire, smoke and sulfur. 18 A third of mankind was killed by the three plagues of fire, smoke and sulfur that came out of their mouths. 19 The power of the horses was in their mouths and in their tails; for their tails were like snakes, having heads with which they inflict injury. (Revelation 9:13-19)
In this passage we see that God will judge the world by releasing some sort of horrible curse near the Euphrates River. There will be an army of 200 million “mounted troops” that will kill one third of the world’s population. I believe that these forces will drive towards the Euphrates river, which will act as a natural barrier to them, at least until it is dried up (see Revelation 6:12) Therefore I envision this army sweeping through the Asian mainland between the Euphrates River and the Pacific coast. It will be easy for this army to kill one third of the world’s population in this area. Indeed, over half the people in the world live in Asia, and over a third live in China or India.
But who are the horsemen? Some believe that they are an army of demons. This is very possible. But it is also possible that they are humans. It is very possible to raise an army of 200 million out of Asia. Also, the “horses” pictured here could easily be armored mobile artillery (i.e tanks). John’s description of them is pretty good, for someone who has never seen a tank before or self-propelled artillery before. Their “mouths” which spew forth “fire, smoke, and sulfur” would be their main cannon, whereas their “tails” would be their secondary weapons, perhaps a machine gun. I have no idea, though, exactly what it means when it compares their tails to snakes. Perhaps John is trying to describe some sort of weapon that has not been invented yet.