I have something I would like cleared up about Regiment number designations. Does the numbering proceed from the total number of Regiments from a world or by the type of Regiments from that world?

For instance, let's say a world was founding it's first twelve regiments ever. The first nine are Line Infantry, the tenth and eleventh are Mechanized Infantry, and the final regiment is an Armoured Regiment. Would they be:

The 1st-9th Infantry, the 10th-11th Mechanized, and the 12th Armored

OR

The 1st-9th Infantry, the 1st-2nd Mechanized, and the 1st Armored.

Anybody know the answer?

When it comes to details such as these, 40k leaves them deliberately ambiguous or provides conflicting information. Even aside from authors regularly disregarding what other official sources have written on the subject before them, there is the in-universe issue of many worlds handling things differently due to local tradition.

In short: it's up to you. The only thing I have seen with some regularity is that regimental numbers are often treated like honorifics and basically "inherited" by newly raised units, meaning that as soon as the "187th Tundra Wolves" get destroyed, Valhalla would raise another regiment that takes over that name.

Oh, speaking of examples in regimental names - you could look at various regiments in official material and extract from there, too. From what I have seen it's not very common to actually list the regiment's type in its name, but instead you get a combination of homeworld + number, and sometimes a sort of byname.

Some examples from the 5E Guard Codex:

• Valhallan 1212th "Cold Bloods"
• 339th Armageddon Steel Legion "The Iron Heads"
• 9th Vostroyan Firstborn "Old Irascibles"
• 3rd Mordian
• Cadian 8th "Lord Castellan's Own"
• Catachan VII "Catachan Devils"
• Catachan XVIII "Swamp Rats"

"Upon their initial founding, regiments are identified by the name of their homeworld and a humber - for example the 144th Cadian Regiment is the one hundred and forty fourth regiment to have been raised on the fortress world of Cadia. It is not uncommon for a regiment's number to be recycled following its destruction, a new raising taking the designation of their predecessor. In this way, the regiment is re-founded, the new recruits tasked with upholding its honour and traditions. Indeed, the Vintor 823rd serve the Emperor to this day, despite being wiped out on more than nine different occasions in the span of a single decade. In addition, regiments are often given unofficial names, either inherited and therefore part of tradition, or else earned on the field of battle."

- 5E C:IG p8

Thanks for your reponse. The quotation from the 5e IG codex suggest the Cadians handle it like mu first example, and since they tend to be the sort of Standard upon which other worlds model themselves, I'll go with that.

I believe it is total. The many references often mention a regiment, but not as often what sort they are. For instance, if you are a fan of Tactical Genius (Creed), you know he is from the Cadian 8th. Nowhere that I remember reading do they tell us, for sure, if it is infantry, mech infantry, a scout unit... I believe that it is just "this is the 101st regiment. We have formulated it to..." I can't say this with certainty; only my own certainty, as it is how I use it. When I formulated my 1st Lokarin, they were comprised of the survivors of 1981st Cadian (a mechanized infantry company with decent tank access, though not at the time of forming the composite regiment), and the 103rd Elysian (a drop unit of scouts). I pulled the numbers out of the usual place, and choose to assume that, for something as vast as the Guard, numbers are just there. Tau? Those numbers in their suits matter, and Space Marine companies, too, but not the Guard, at least not as I see it.

Nowhere that I remember reading do they tell us, for sure, if it is infantry, mech infantry, a scout unit...

Page 14 of the 5E Guard 'dex also calls it the "Cadian 8th Infantry Regiment" - but the suffix is not commonly attached. Most often it's really just "Cadian 8th", which just would not work if there was also a "Cadian 8th Armour Regiment" etc.

It's also the same for the Space Marine Chapters, which are divided into Battle and Reserve Companies, yet those still follow a single numerical listing as well.