Armageddon is only mentioned ONCE in the entire bible; Rev. 16:16.
One of the major things that I've come to understand, is that the book of Revelation was in all pretenses fulfilled during the first century.
The actual word "Armageddon" only occurs this once (Rev 16:16). But the ideas encompassed in the word and in the verse and context are not new, not by any stretch.
The idea that Jehovah would gather all the nations against His people for a final confrontation occurs a number of times in the OT Scriptures: For example, Ezek 38:1-9; Zech 14:1-2.
Bobcat is absolutely correct in his statements here and more, and is standing on very solid scriptural ground. In fact while the Apostle John happens to use the term Armageddon here in Revelation 16:16 when prophesying about this particular occasion on which God would express his wrath upon his enemies, in other passages he uses the term "the great day of God the almighty," "bowl of God's anger," or even "hour of his judgment." (Re 14:7 16:1) Moreover in OTHER books of the Bible, ones such as Paul or even Jesus himself opt for terms such as "day of Jehovah" or "a conclusion of a system of things" in connection with these foretold times of Jehovah's vengeance against his enemies. (2 Th 2:1-3) (Mt 13:39)
As we can see here in these last two scriptures alone, these occasions of God's wrath upon his enemies are synonymous both with "apostasies" of his appointed shepherding class as well as the subsequent "harvests" of these very same "firstfruits" that are always required to restore the "kingdom covenants" which are always broken with these "apostasies." (Lu 22:29) (He 9:16-18) This is precisely the reason the earth experienced the conclusion of the Jewish system of things a few decades after the "harvest of the firstfruits" (death and resurrection of Jesus himself on this occasion) or spiritual cleansing (baptism) and rebirth ("coming") of the nation/kingdom that occurred in 33 CE. (Col 1:13) (Re 14:4 20:6)
This information alone already produces a CONUNDRUM of problems with the notion of Revelation being fulfilled completely in the first century. The first problem here would be the fact that the Apostle John happens to be uttering this prophecy of Revelation at the very END of the first century. This fact alone would absolutely preclude the possibility of all its prophecies being fulfilled WITHIN this particular time frame. But this is only the BEGINNING of the problems with this idea.
For example we find here in Revelation that John is foretelling FUTURE occasions in which these national apostasies or complete spiritual "killings"/"conquerings" of God's "holy ones" would occur, along with (as always) their corresponding "harvests" and "bowls" of God's anger." (Re 11:7, 11-13, 18 12:5 13:7 14:15 16:1, 14 19:17-21)
ALL these things were being PROPHESIED by the Apostle John around 96 CE. CLEARLY all these foretold events were not to be fulfilled within the next three years or so, and PARTICULARLY since we have certainly not experienced the paradise earth that is foretold in Revelation 21, or for that matter the Millennial Reign (which would obviously span more than three years) and the complete annihilation of Satan and the demons soon to follow foretold in Chapter 20.