1000 men strong: The size of a chapter never bothered me before, but a post on here talked about how another 0 should be added to make it 10,000 marines, and the old legions should have had 800,000+ marines. It made so much sense, and I cringe a little bit every time I hear about only 1000 marines. That's really not a big number at all, and even 10,000 in the grand scheme of things isn't big either.
Absolutely agree. Considering the massive casualties space marines take in every mission in the great crusade (as described in the FW books) and the fact that the legions and equipment was better back then and they were led by the Primarchs I'm astonished that Roboute Guilliman thought that 1000 marines was a suitable size for the future Chapters..
Given the fact that the Chapters are now used as pure assault forces or last ditch defence forces rather than armies, both of these are where you take the majority of casualties and therefore the Chapters would simply die out as you wouldn't be able to replace the losses you'd take quickly enough. All the better (in my opinion) novels describe how many casualties the Chapters take and the Imperial Armour books also show the Chapters taking large casualties (such as in the Badab wars and the siege of Vraks books).
If the Chapters continually take such casualties (and considering I doubt they'd turn their backs on a situation where they were needed) they would be ground down in no time.
If anything needs retconning it's the 1000 limit. I understand the reason for splitting the Legions but by splitting up the Chapters to be so small they're now basically incapable of their primary purpose which is to be the elite forces of the Imperium. All an enemy needs to do is to simply fight a battle of attrition and sooner or later the chapter will need to either retreat or risk being wiped out. Alternatively if they only send 1 or 2 companies to avoid the chapter being wiped out then I'm sorry but enemies can simply overwhelm them.
Enemies such as Necron can outlast the chapters by being tougher and Tyranids can simply send more forces and you get what happen with the Scythes Of the Emperor where their home planet was destroyed. I can't remember the Chapter who were destroyed when a Necron tomb awoke on their homeworld but the result was the same and simply goes to show that the Chapter as a unit simply isn't strong enough to achieve what is needed and that's when it's deployed as a whole. Company sized units are even weaker.
The Damocles Crusade is another example where 2 first founding chapters (Ultramarines and Iron Hands) and the Scythes of the Emperor, supported by Imperial Guard and titans were stopped cold by the Tau when the battle descended into one of attrition. The Ultramarines were led by Marneus Calgar who in the fluff is one of the most brilliant strategists of the age and yet the Imperium still couldn't force a victory. This leads me onto my second thing I hate.
As someone said "A war run by committee is a war already lost" (I'm paraphrasing as I can't find the exact quote but I think it's in Gaunt's Ghosts somewhere). The splitting the Imperial Armed Forces so much it has turned every crusade, every defence into a battle run by committee where the Imperial Commander has to beg and please with the Space Marines and Titans to do what he/she needs them to do.
Putting the Space Marines and Titan Legions outside the overall command structure is just insane. Most of the time the Chapters simply don't bother to co-ordinate their attacks with the allied units and when they do the Imperial Guard commander has no-authority over them and neither does the Space Marine commander over the Imperial Guard forces. The expression "the left hand doesn't know what the right hand is doing". The way I see it, when Space Marines and Imperial Guard fight on the same planet they almost act as 2 completely independent armies who happen to be fighting the same enemy. WTF? The enemies of the Imperium must be laughing. Divide and conquer is an ancient strategy and the Imperium divides itself by choice? No wonder the Imperium is on it's last legs. It's overall military command structure is completely ill designed for what it needs to be.
Only when Space Marines or the Guard fight on their own and therefore there is a unified command structure (such as during the defence of Ultramar against the Tyranids and later Honsou) can a truly effective battle be fought and even then the weakness of the Chapters are cruelly exposed once more. The only crusade I'm uncertain about is Macharius' crusade and whether there were Space Marines with him and how they operated as Macharius' crusade was undeniably effective and I would love to know how and why?