Quote Originally Posted by The Glyphstone View Post

A Warband is not the size of a Loyalist chapter. Read the page you actually linked to...

tens or hundreds = 1,000 members of a Chapter-size unit

50 * 1000 = 50,000 maximum, if 50 whole chapters went rogue.

When you link to sources,make sure those sources don't actually contradict your claims next time.
Quote Originally Posted by Lexicanum
The Legions were massive armies, and the size of each could vary tremendously. A precise number was never truly achieved and maintained. Even during the Great Crusade, some Legions were very numerous, while others were not. The numbers would always vary with new recruits and inevitable battle-losses, and also important was the availability of potential recruits and the administrative skills of the Primarch and his officers.
You appear to be referring to Chapters of space marines, i.e. post-heresy legions broken apart by the changes made by rowboat girlyman (roboute guilliman) in the Codex Astartes.

Pre-Heresy Legions varied wildly in size but the average was 'about 10,000'. So depending on the specific size of the 20 Chaos Legions, it could have definitely involved hundreds of thousands of space marines AND daemons.

And yes. People fapping about space marines have spouted wild, wild numbers and fantasy scenarios and everything else that doesn't really jive with the technology level or the perceived results of the space marines. Portraying guardsmen as weak and inferior and useless and 5-10 space marines being able to single-handedly wipe out xenos fleets and the whole imperium being held together by tiny numbers of space marines is a common 'view' of the setting.

That said, it makes much less sense and is less of a working setting and more of a weird power fantasy about big armoured men who are soooo cool and strong than anything else.