Pre-Codex / Heresy Era Marine Training

[Polaria]

I've been reading through much of the Horus Heresy series and from what I've read so far there is no mention of Scouts or Devastators at all. There are obviously the "regular marines" (Tactical equivalent) and then some Legions have Assault Squads and some sort of heavy weapon guys but the Scouts seem to be missing out totally. As the Codex-approved training path of Space Marines later in the 40k era is Scout > Devastator > Assault > Tactical I wonder how did recruits become Marines in the 30k era?

[Lupe]

I suppose each Legion had its own traditions concerning recruitment.

Given the size of the Legions and the fact that the Imperium was not beset on all sides by enemies, I doubt there would have been any pressing need to deploy marines without their full implants. The fact that they could better spend their time training in matters of tactics, strategy, planning, logistics or even fire drills would have made a lot more sense in the context of an Imperium who had almost rid itself of any outside threats. That would explain the fact that Scouts are not even mentioned in the books.

Devastator, Assault and Tactical marines aren't ranks, they're just specialized roles. They didn't even need to be named this way back then, since the Legions were all proud of their own traditions and terminologies. And there was certainly less of a need for specialized squads, when the Legions had access to far more ample supplies of whatever weapons they needed on a case-by-case basis. The emphasis was probably on allowing the individuals to outfit themselves with appropriate gear for every deployment, based on whatever they were more comfortable with, since statistically there was a significant chance for complementary weaponry to be carried by a nearby brother anyway. Besides, the Astartes relied on weight of numbers a lot more back in the old days, so there wasn't that much of a need to tailor individual squads to deal with specific threats.

However, when the legions were split, it was expected that every individual chapter should cover large stretches of space, which meant that they would have to split their limited numbers across several battlefields at once. That meant the need for a core of tactically flexible troops, with some highly specialized support squads, in order for small-scale deployments to be viable.

Now, you've split all the remaining loyalist legions int chapters a thousand strong. Each of these legions had specific titles and ranks before, and some chapters (former companies, most likely) even had such a lexicon of their own. So, it made sense for Guilliman - who had already compiled and standardized a comprehensive list of tactics, strategies and policies, then widely distributed it for the use of these new chapters - to introduce specific terms to designate specific roles, because the whole idea of chapters was that they would operate independently for as long as possible, but converge to support each other every so often when the need arose. Having to figure out what a chapter you have never fought with before calls the guys with heavy bolters in the middle of an Ork charge is an impediment. So, these standard designations were simply included in the first chapters Codex Astartes in order for the guidelines contained later on to make sense.

[Polaria]

I checked my books again and found a mention of Scouts in the beginning of Deliverance Lost where the Raven Guard is being re-organized after Isstvan V. The organization was:

'Talons' - Tactical companies. Majority of the legion.
'Falcons' - The survivors of the various assault platoons, along with several Dreadnoughts.
'Hawks' - Handfull of bike squads, land speeders and aircraft crews along with existing scouts.

Furthermore Corax said that they would not use any more Scouts in the organization, but instead put new recruits into power armour and introduce them into 'Talns' as soon as they had been fully implanted. This would imply that before then they had scouts, but doesn't tell if they were only training scouts or using them in battle also. The interesting thing is that Assault platoons are mentioned as being different from Tactical companies.

[Lupe]

Well, damn. I totally forgot about that part.

I guess they did exist, but, there's no mention if they were used by all the legions. Then again, if any legion had a reason to use them, it'd be the Raven Guard. After all, if your key strategy consists of guerrilla warfare, you'd want to give your guys a head start on the finer points of stealth before throwing them into battle in a quarter ton of noisy power armour...

However, even if the practice of scouts was restricted to the Raven Guard and Alpha Legion at the time, the Codex Astartes has the great merit of compiling the successful elements of multiple legion doctrines (both loyalist and traitor) and disseminating the information evenly among the newly formed chapters. Part of these stipulations of the Codex Astartes were probably mandatory, and these were likely the survival stratagems that had proven the most successful among the battered loyalist legions.

[baphomael]

The collected visions book has a few images of "Recon Marines". Some are clad in power armour and equipped with lasguns, while others have been depicted in scout armour.

Aside from those images, there's no other info as far I know. Could be that Recon marines are dedicated scout/Recon troops rather than neophytes in training... akin to wolf scouts. Then again, it could vary from legion to legion... afterall, as noted the raven guard had scouts at one point.

[Inquisitor Engel]

It seems from reading "The Crimson Fist" that the Imperial Fists had modern Marine-esque trials on Inwit before they'd actively recruit new Marines, as both tests of character and strength. It seems the Dark Angels/First Legion looked more for biological suitability, perhaps following the mantra that "more is better."