Hey All,
question - is it normal that I am regularly faced with oppising ground unit forces of more than 200,000 tons? How do you win these invasions? With the additional bonus from fortifications I see myself sometimes throw 5-7 times the amount of tonnage at these units and they still barely make a dent (maybe they kill 50,000 tons or so). What are your normal invasion force sizes?
I normally attack with a mixture of infantry (ca. 60% of my force), light vehicles (ca. 20%) and heavy vehicles (20%). Logistics support is in light and with individual infantry in each subformation.
Thing is you aren't actually fighting 200,000 tons. 200k tons is what your active sensors see, the rest are hidden by their fortification level. This means that depending on their fortification that 200k could be more like 1,000,000 tons of ground forces. Which according to the amount that your bringing would be a 1-1 matchup, which an attacker will certainly lose because of the combat benefits of fortification. The good news though is that the 50,000k that you killed probably translates to a lot more than you think because of that exact same reason.
As for your army itself. I like having infantry in my attacking forces mostly due to RP but as far as game mechanics go, infantry, even with genetic modding are very suboptimal at attacking unless there is some terrain bonus that they can take advantage of (jungle training, mountain training etc.). Most will recommend that you spam light-medium-heavy vehicles as the primary consideration on the attack is not cost but also shipping tonnage.
Vehicles are also much more survivable on the attack than infantry because when attacking, the fortification bonus that infantry get doesn't exist. Instead, every unit has an evasion chance when attacking:
Infantry and medium vehicles have 60% to hit chance
Light vehicles have 40% to hit chance
Heavier vehicles have less evasion in general.
Combine this fact with vehicles having more hitpoints and armor and you end up with a much more survivable force than a mostly infantry attacker.
Finally, technology has a massive effect on the progression of battle, in particular ground combat armor. If your technology is reasonably further ahead than the enemy, the ratio of troops that you have to send will drastically drop.
To get to your scenario, what you have here is actually somewhat on the low side. You can expect an NPR homeworld to have tons more. 5-7 times the ground forces is usually a good bet against the
actual size of enemy forces unless they are jungle mountains or some other stupidly strong terrain in which case its more like 15 times. I think the problem you have is that you didn't know that fortification obfuscates the true size of the enemy so you brought a force that could defeat the forces you saw but not the ones that were actually there. So try bringing 6 million tons next time and I think you'll do better.