Step still to come (one reading among others)

Armageddon and final confrontation

**Artist’s impression** The Rider and the armies of heaven confront the beast and the assembled kings of the earth (Rev 19:19), artist’s impression from an English illumination (c. 1255-1260). A scene to come. — Anonymous English illuminator — Dyson Perrins Apocalypse (J. Paul Getty Museum, Ms. Ludwig III 1), c. 1255-1260, Wikimedia Commons · Domaine public

? Not yet happened, no date

See the full entry: sources, objections, answers

In short

The announcement. John, in the book of Revelation, toward the end of the 1st century, announces that armies are gathered at a place called in Hebrew Armageddon, then that a rider named “Faithful and True” comes out of the opened heaven and wins the final victory.

What happened. This has not happened yet. In the account, the gathering takes place during the bowls, and the rider's victory comes afterward.

What is still debated. the scene of the birds summoned against Gog in the book of Ezekiel looks very much like the one in Revelation, but we do not know whether it is the same moment.

The text (World English Bible)

He gathered them together into the place which is called in Hebrew, “Harmagedon”.
Rev 16:16

I saw heaven opened, and behold, a white horse, and he who sat on it is called Faithful and True. In righteousness he judges and makes war. His eyes are a flame of fire, and on his head are many crowns. He has names written and a name written which no one knows but he himself. He is clothed in a garment sprinkled with blood. His name is called “The Word of God.” The armies which are in heaven, clothed in white, pure, fine linen, followed him on white horses. Out of his mouth proceeds a sharp, double-edged sword that with it he should strike the nations. He will rule them with an iron rod. He treads the wine press of the fierceness of the wrath of God, the Almighty. He has on his garment a…
Rev 19:11-21