Step still to come (one reading among others)

Second seal — peace taken away

**Artist’s impression** The rider of the red horse receives a great sword (Rev 6:4). Illumination from the Bamberg Apocalypse (c. 1000); a scene announced by the text, not one that has happened. — Anonymous illuminator (Reichenau school), Bamberg Apocalypse, c. 1000, 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, sees come out, at the second seal, a red horse whose rider receives a great sword and the power to take peace from the earth, so that people kill one another.

What happened. This has not happened yet. In the account, this scene follows that of the white rider and comes before that of the famine.

What is still debated. nothing in the text requires a single world war declared on the same day: it may be conflicts that gradually worsen.

The text (World English Bible)

When he opened the second seal, I heard the second living creature saying, “Come!” Another came out, a red horse. To him who sat on it was given power to take peace from the earth, and that they should kill one another. There was given to him a great sword.
Rev 6:3-4