^ As I've heard MoO 3. had an interesting ground combat system.
Long time MoO3 player and veteran member of the now defunct MoO3 community and modding enterprise here.
Yeah, along with many other aspects in the game, MoO3 had an interesting ground combat system. It went something like this...
Races all had ground combat ratings based on their inherent biology, relating to toughness, reactions and so on. Each species had a preferred combat environment relating to gravity, terrain and atmosphere. There were a variety of ground combat units dependant on if you knew the techs, each further augmented by bolt on ground combat techs relating to weapons and armour. As an empire could be made of more than once species, it was more than feasible to have multi race armies, with high initiative human marines supported by high hit-point Bulrathi armour fighting alongside one another.
To initiate ground combat you had to get drop-ships loaded with troops into a planetary system and overcome any space or orbital defence and unload them onto a planet, normally after bombarding it. Ground combat began with an overview of the forces facing off, and an overview of where the combat was taking place in terms of type of planet and terrain. Usually, the invading force would be a well equipped yet relatively inexperienced force of varying units, and the defenders would be a rag tag assortment of militia, and whatever units had survived the bombardment. You then had to pick a combat strategy such as ambush, flank, mass assault and so on... each offensive and defensive strategy gave bonii and malii to your combat attributes, and operated a little like scissors/paper/stone. As such, you had a complex multi-faceted system that looked to take into account many things when modelling the ground element of interplanetary war. It was more than possible for a rag tag band of humans to fight of the invading aliens of superior tech level if the environment did not suit them and you picked the best defensive strategy for the units/weapons/environment/races, and in theory should have made you think if invading the high G gas giant homeworld of a race was worth it or even feasible with the forces and tech at your disposal. I found myself setting up specific combat units of various races with specific types of combat in mind.
Alas, like most other things in MoO3, it was broken. The spreadsheets that underpinned the ground combat routines were a mess. Various properties and functions were mislabelled or mathematically wrong so it really did not matter what units of what race you had with what weapons or what stratagem, as there were no working variables, and the AI would never actually attempt to invade due to how it handled fleet management. It took literally years for us to track down each and every single problem in the code, and restore and enhance the intended functionality. But when it was fixed - boy was it beautiful. One notable playthrough had me as a human empire that enslaved a cybernetic race. Said cybernetic race was used to churn out millions of ground combat units that swarmed the known universe thanks to their high environmental tolerance and decent toughness. What they lacked for in smart initiative based fighting they made up for in raw numbers, enhanced by generally following mass assault tactics and allowing for high collateral damage with nuclear, chemical and biological agents allowed in combat. They only ever had difficulty against races with high inherent toughness, but throwing enough troops at them worked in the end.