Caroline:
See my posts # 932 & 933 on this thread for an alternative view of the sheep & goats parable, which would impact the question of 'Who would survive the battle of Armageddon.'
This view might also be hinted at in Rev 11:18 -
"And the appointed time for the dead to be judged, and to give [their] reward to your slaves the prophets and to the holy ones and to those fearing your name, the small and the great, and to bring to ruin those ruining the earth."
"The holy ones" is mostly used as a designation for God's people. So the addition of "those fearing your name, the small and the great," may allow for something similar to the 'vast mixed company' of Egypians who left Egypt with Israel.
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On the question of who will do the killing:
"Armageddon" is a "place" (whether symbolic or literal). According to the way Rev 16:16-21 delineates events, "the kings of the entire inhabited earth" are "gathered" there during the sixth bowl of God's anger, which is prior to the outpouring of the seventh bowl of God's anger (v. 17). The results of that seventh bowl include the "great earthquake," which includes the events described in Rev 16:19-21.
The only ones in that sequence of events directly affected by "heaven" are the ones in verse 21 who are pummeled by the hail. These correspond with "the rest" who are "killed off" by 'the king riding the white horse' (Jesus) in Rev 19:21.
"The great city" of 16:19a being split into three parts, if it is in fact an allusion to Ezekiel chapter 5, represent God's unfaithful people who receive judgment from God, but at the hands of humans.
The 'falling of the cities of the nations' of 16:19b may very well hint at much loss of life. It is parallelled in Matthew 24:29 and Luke 21:25, 26, which in the first century saw its fulfillment in the vast and bloody Roman civil war of 68-69 AD.
In Revelation 16:19, the 'falling of the cities of the nations' is a prelude to God's handing "Babylon the Great" his 'cup of wrath.' But chapter 17, which describes that judgment on "Babylon" has 'the ten horns and the wild beast hating the harlot' and doing her in. The 'hatred' of her may very well come from the events that precede her judgment (the falling of the cities), indicating some implication of the harlot in the preceeding events. At any rate, the actual killing of the harlot is described as being at the hands of humans.
The 'removal' of the 'mountains and islands,' being bracketed by Babylon's judgment before and the hailstorm after, would logically be "the war" described in Rev 19:19, 20. Even though in that account they (the kings of the earth and their armies) are described as being defeated by the rider of the white horse and his armies, other Bible accounts of this battle have them being killed off (at least in part) at their own hands (Compare Ezekiel 38:21-39:4; Haggai 2:22; Zechariah 14:13).
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On the question of who will be resurrected:
John 5:28, 29 describes those in the "memorial tombs" as "those who practiced good things" and "those who practiced vile things," which appears to be a merism.
Acts 24:15 similarly describes the resurrection as including "the righteous and the unrighteous." (Possibly another merism.)
1 Cor 15:23 describes them as "those who belong to the Christ," which, when compared with John 6:51 where he gives his "flesh in behalf of the life of the world," could conceivably include very many of humankind.
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I admit that this is not necessarily the published WT point of view. So whether "JWs" in general would agree with me is a question. (I think more likely most JWs would fall back on whatever the most recent published WT viewpoint is. Not all, but most.) But I hold that the above is an accurate exposition of what the scriptures cited above relate. Those scriptures would serve for me as "evidence" based on my holding of them to be the word of God. Whether they serve that way for others is something they would have to say.
Take Care