True - that the view of Armageddon, the second coming , the millennium etc - was very different for Millerites than it is for Seventh-day Adventists.
And it is also true that the 7 plagues of Rev 16 are all future. So the 6th Plague calling for Nations to gather real armies to a real location to fight a real battle -- is very literal. And we see all of that literally "assembled" in Rev 19. Where literally two armies meet according to the chapter - at the appearing of Christ.
But I think we can all agree that this battle will begin with the gathering at the sixth plague where we see the “water” of the “great river Euphrates” will dry up in order to prepare the way for the “kings from the east.” Then we see coming out from the mouth of the dragon, the beast, and the false prophet “three unclean spirits” which make signs to seduce the “kings” of the “whole world” and to gather them together at the place given as “Armageddon” which will battle between heaven and earth, between Christ and Satan. A final effort by the part of the evil to incite the world to fight against God and wipe out and annihilate the people of God with what will end as a military attempt to face Jesus and the angels at the second coming. The sixth plague merely announces the preparation of the earthly powers or evil with the "spirits of devils" gathering the "kings of the earth", and the "whole world", for the actual battle of Armageddon.
Revelation 16:12-15
12 And the sixth angel poured out his vial upon the great river Euphrates; and the water thereof was dried up, that the way of the kings of the east might be prepared.
13 And I saw three unclean spirits like frogs come out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet.
14 For they are the spirits of devils, working miracles, which go forth unto the kings of the earth and of the whole world, to gather them to the battle of that great day of God Almighty.
15 Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walk naked, and they see his shame.
16 And he gathered them together into a place called in the Hebrew tongue Armageddon.
Now begins the actual battle, as the battle itself “will take place during the seventh plague which clearly is the Second Coming opening with God declaring "It is done". So the sixth and the seventh plagues are the two consecutive
stages in which Armageddon event will begin and the take place with a great and mighty earthquake that will rend the earth and we see “noises and thunderings and lightning” as well as “great hail” and then we have subsequent fall of Babylon the great. The devil knows it foretells his soon coming end is approaching, so strives to wipe out the saints, but Christ comes to help his remnant and deliver them from the oppression against them here on earth by Babylon and the earthly powers supporting her.
Revelation 16:17-21
17 And the seventh angel poured out his vial into the air; and there came a great voice out of the temple of heaven, from the throne, saying, It is done.
18 And there were voices, and thunders, and lightnings; and there was a great earthquake, such as was not since men were upon the earth, so mighty an earthquake, and so great.
19 And the great city was divided into three parts, and the cities of the nations fell: and great Babylon came in remembrance before God, to give unto her the cup of the wine of the fierceness of his wrath.
20 And every island fled away, and the mountains were not found.
21 And there fell upon men a great hail out of heaven, every stone about the weight of a talent: and men blasphemed God because of the plague of the hail; for the plague thereof was exceeding great.
We then in the next chapter, see the earthly powers supporting Babylon laid out for one prophetic hour, but they see the truth of Babylon on turn on her.
Revelation 17:12-18
12 And the ten horns which thou sawest are ten kings, which have received no kingdom as yet; but receive power as kings one hour with the beast.
13 These have one mind, and shall give their power and strength unto the beast.
14 These shall make war with the Lamb, and the Lamb shall overcome them: for he is Lord of lords, and King of kings: and they that are with him are called, and chosen, and faithful.
15 And he saith unto me, The waters which thou sawest, where the harlot sitteth, are peoples, and multitudes, and nations, and tongues.
16 And the ten horns which thou sawest upon the beast, these shall hate the harlot, and shall make her desolate and naked, and shall eat her flesh, and burn her with fire.
17 For God hath put in their hearts to fulfil his will, and to agree, and give their kingdom unto the beast, until the words of God shall be fulfilled.
18 And the woman which thou sawest is that great city, which reigneth over the kings of the earth.
In Revelation 18 Babylon is described in greater detail and the call made to come out of her, and the warning given that "God hath remembered her iniquities."
Revelation 18:1-5
1 And after these things I saw another angel come down from heaven, having great power; and the earth was lightened with his glory.
2 And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.
3 For all nations have drunk of the wine of the wrath of her fornication, and the kings of the earth have committed fornication with her, and the merchants of the earth are waxed rich through the abundance of her delicacies.
4 And I heard another voice from heaven, saying, Come out of her, my people, that ye be not partakers of her sins, and that ye receive not of her plagues.
5 For her sins have reached unto heaven, and God hath remembered her iniquities.
Then in Revelation 19 we see Christ as He comes to earth to fight the kings of the earth and the wicked of the world, and describes what the end is for those who have the mark of the beast, and the "beast" and "false prophet".
Revelation 19:14-21
14 And the armies which were in heaven followed him upon white horses, clothed in fine linen, white and clean.
15 And out of his mouth goeth a sharp sword, that with it he should smite the nations: and he shall rule them with a rod of iron: and he treadeth the winepress of the fierceness and wrath of Almighty God.
16 And he hath on his vesture and on his thigh a name written, King Of Kings, And Lord Of Lords.
17 And I saw an angel standing in the sun; and he cried with a loud voice, saying to all the fowls that fly in the midst of heaven, Come and gather yourselves together unto the supper of the great God;
18 That ye may eat the flesh of kings, and the flesh of captains, and the flesh of mighty men, and the flesh of horses, and of them that sit on them, and the flesh of all men, both free and bond, both small and great.
19 And I saw the beast, and the kings of the earth, and their armies, gathered together to make war against him that sat on the horse, and against his army.
20 And the beast was taken, and with him the false prophet that wrought miracles before him, with which he deceived them that had received the mark of the beast, and them that worshipped his image. These both were cast alive into a lake of fire burning with brimstone.
21 And the remnant were slain with the sword of him that sat upon the horse, which sword proceeded out of his mouth: and all the fowls were filled with their flesh.
Then in Revelation 20 we see the sequence of what happens at the Second Coming with the saints it the graves brought up at the first resurrection and taken to heaven to be with Christ in His kingdom and "reign with him a thousand years."
Revelation 20:1-6
1 And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.
2 And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years,
3 And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season.
4 And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God, and which had not worshipped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years.
5 But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection.
6 Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.
And then we see the "dead lived not again until the thousand years were finished" come out in the resurrection of damnation and they continue the attack as Satan deceives and they meet their end against the city of God, the New Jerusalem, in the lake of fire.
Revelation 20:7-10
7 And when the thousand years are expired, Satan shall be loosed out of his prison,
8 And shall go out to deceive the nations which are in the four quarters of the earth, Gog, and Magog, to gather them together to battle: the number of whom is as the sand of the sea.
9 And they went up on the breadth of the earth, and compassed the camp of the saints about, and the beloved city: and fire came down from God out of heaven, and devoured them.
10 And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the false prophet are, and shall be tormented day and night for ever and ever.
