As far as the events of Cadia falling, the Cicatrix Maledictum, and the general storm of destruction we know a fair amount about poster boy armies. We know Blood Angels got nearly wiped, Space Wolves lost their home world, Ultramarines, Scythes of the Emperor, White Scars, Crimson Fists all had chaos rife within their local void space.
However based on readings of the codex I have seen little to do with how the Salamanders fared during these raids and wars. Obviously, we got involved with the Primaris thing with Aggressors helping clear a deamon infested hive world etc. But did we need Primaris? Were they much needed reinforcements to fill holes in our companies and fleets? Or were they simply bulking out our firepower for the ensuing wars to come to support the populous of the Imperium?
A lot of my reasoning for asking is that the Codex is almost deliberately vague on our company structure just mentioning the existence of Battline, Close-support and Fire-support squads, not the number or even an estimate of numbers. (For the purposes of this discussion lets not get involved in the contradiction we've all seen in the Codex concerning number of companies).
Another reason is I'm starting to have a ridiculous number of tactical marine squads available to me (from various friends handing over old models), and I'm questioning if I'm still allowed to say they're all part of the 4th company
Anyway I'll shut up now:
TLDR: Did the Salamanders suffer major losses during the appearance of the Great Rift, or were Primaris reinforcements just bulking out our chapter further?