Sixth Trumpet
Revelation 9:13-15
Then the sixth angel sounded, and I heard a voice from the four horns of the golden altar which is before God,
one saying to the sixth angel who had the trumpet, "Release the four angels who are bound at the great river Euphrates."
And the four angels, who had been prepared for the hour and day and month and year, were released, so that they would kill a third of mankind.
Revelation 9:16-19
The number of the armies of the horsemen was two hundred million; I heard the number of them.
And this is how I saw in the vision the horses and those who sat on them: the riders had breastplates the color of fire and of hyacinth and of brimstone; and the heads of the horses are like the heads of lions; and out of their mouths proceed fire and smoke and brimstone.
A third of mankind was killed by these three plagues, by the fire and the smoke and the brimstone which proceeded out of their mouths.
For the power of the horses is in their mouths and in their tails; for their tails are like serpents and have heads, and with them they do harm.
Revelation 9:20-21
The rest of mankind, who were not killed by these plagues, did not repent of the works of their hands, so as not to worship demons, and the idols of gold and of silver and of brass and of stone and of wood, which can neither see nor hear nor walk;
and they did not repent of their murders nor of their sorceries nor of their immorality nor of their thefts.
The Euphrates River location plays a part in this war. It would seem to start around there and move out from there to other regions. It looks like it could be an extension of current War in Iraq, but may happen some time later, if perhaps a radical group gains the government of Iraq.
The number of people taking part in this war is stated as the number of armies being 200 Million. In this conflict a third of mankind is killed (in this area?) would amount 66.6 Million from the armies. A third of the whole would be much more and be a couple of billion.
The weapons of modern warfare are seen described here.
The modern tanks and their fire power. At the time of the vision, there was not known anything to do with gunfire and cannons or large artillery shells and so forth. Ironically, the modern word for triggering a weapon is the word "FIRE". It is also used descriptively as weapons firing and even conflict between opposing soldiers as fire fights.
The side effect of a weapon being fired is that it shoots out fire out of the barrel, along with smoke and the residue of the propellent including the smell of burnt propellent. With gunpowder, the major smell left over is that of sulphur the modern name of the ancient word "brimstone".
The colours of the tanks and Armoured Personnel Carriers (APCs) are described as fire, hyacinth and brimstone. Sulphur/brimstone is yellowish in colour. Very much the colour of the desert camouflaged armoured vehicles. (verse 17) Also the heads like lions may well refer to the roaring noise that the Head/front guns make when they fire out of their "mouths".
The Bradley Fighting Vehicle has forward big guns (not as large as tanks) and carries troops in its tail, which has a tail gate that opens up so they can be deployed. Generally when they exit they take cover, and lie on their bellies, and move along the ground wiggling much like a snake, fitting with the description given. (verse 19) There are a variety of Bradley's designed for specific tasks, from a traditional APC look to a having rockets on their turrets as in the line backer models.
As these events will not be recognised by many as being the fulfilment of prophecies, many will continue as they have in their sinful ways. Many in religions which have compromised in the name of "equality" will continue to adhere to the false doctrines which go against Scripture. (verses 20 & 21)