After a period of "ohgodwereallgonnadie" that followed the discovery that there was an entire squadron of hostile alien warships sitting in a system right next door from Sol while I not only had no armed ships, but hadn't even researched any military technologies, the Terran Dominion can finally feel itself secure enough. Luckily, the xenos didn't bother to survey that one system more, which gave me the time to close the tech gap and build a fleet. Now, however, the Dominion is learning that crossing interstellar distances in the blink of an eye, harnessing the energies of stellar cores and confronting armadas of ships that could obliterate entire worlds are all rather trivial pursuits next to the challenge of moving some dudes and their stuff around. The 18000-tonners that can keep space free of even the mightiest alien vessels are dwarfed by the monsters I need to make sure that ground troops land safely under fire from STO batteries. Over fifty thousand tons of dropship are required to move a single battalion, and I need five of those blasted things for a brigade. It'll take years just to build enough maintenance facilities to keep them from falling apart. And in the process of designing my ground troops I realised just how much supplies a brigade consumes. If the fighting takes more than two weeks, my soldiers will be down to finger pistols and shouting "bang!". I could make a large "supply dump"-type HQ, but it won't fit in a dropship. I'd have to make the ship even bigger, but a) that would be an engineering challenge (make it fast enough, durable enough, spacious enough), b) it'd take yet more time to expand the shipyards and build the darn thing. I could set up a series of smaller supply HQs, but that makes for a really ugly command chain and doesn't save me from building a lot of additional dropship tonnage anyway. And all this for a single brigade. What must it look like when you drop multiple divisions to take a hostile homeworld?! Ugh. Logistics while the enemy has anti-orbital firepower are a female dog.
How big are your batallions? Or brigades?
For me a brigade is a little less than but no more than 100k tons, a company is 3000-3500 depending on type, battalions at most 15000 and regiments 30 to 40k tons. The largest organization ive made is a division which is about 500k tons total. I need around 34 30k ton armoured transports in order to carry the whole thing. Transport convoys get really big really fast unless you want to have 200k ton behemoths.
Would you mind giving a rough breakdown of your formations? I've tried basing my formations off of US Army formations, and my companies are only about over 1k, with Battalions around 5k and Brigades around 25k.
My military organization goes down to the company level which are the actual combat units. An infantry division looks like this:
Division HQ (500k)
3x Infantry Brigade (100K)
2x Infantry Regiment (40k)
2x Infantry Battalion (15k)
1x Spec-ops company (ATK-3250)
3x Infantry company (DEF-3250)
1x Support artillery section (SUP-1500)
1x Motorized Regiment (40k)
2x Motorized Battalion (15k)
1x Mechanized company (ATK-3500)
3x Motorized company (ATK-3500)
1x Mechanized Brigade (100k)
3x Mechanized regiment (40k)
5x Mechanized Battalion (15k)
4x Mechanized company (ATK-3500)
1x Light Mechanized Battalion (15k)
2x Mechanized company (ATK-3500)
2x Motorized company(DEF-3500)
1x Armoured Regiment (40k)
2x Armoured Battalion (15k)
1x Mechanized Company (ATK-3500)
2x Armoured Company (ATK-3500)
1x Medium artillery Battery (SUP-3500)
1x Artillery Regiment (40k)
2x Artillery Battalion (15k)
1x Heavy Artillery Battery (REAR-3500)
2x Medium Artillery Battery (SUP-3500)
1x Motorized Company (ATK-3500)
4x Logistics Battalion (LOG-15k)
Note that because of the way the brigades are designed they can be detached from the main division hierarchy and still function properly - with a defensive and offensive line. The numbers in brackets are HQ ratings and for combat units their size and typical field position. The actual size of a division on average hovers around 450k so individual support components such as the armoured and artillery regiment can be slotted in order to steer the division in a particular direction or kink.
If you are trying to base your formations off of real ones - do not do it through tonnage, do it by the no. of men. I just looked at the "military organization" wikipedia page and saw that companies had anywhere between 80-250 men. So I aimed at 250 men and a size of 3250 tons came about relatively naturally.