I played this game on one of those free video game demo CDs you would find in old gaming pc magazines. I believe it was on a cd I also played a grim fandango demo on and MAYBE mechwarrior. So this would prly be around late 90's and early 2000s.
It's an RTS with at least two "armies" or "factions".
It was very tank/armour oriented. I don't recall ANY infantry or air. However, it was only a demo cd so I probably did not get to see even half the units in the game..
There were clearly humans you would play as (basically terran from SC) against aliens. The aliens were very green. The aliens looked a lot more organic compared to the mech humans you play as.
In the demo there were only 2 structures/building. One for you and one for the enemy aliens. I drew a picture of what some of the alien donut tanks looked like lol:
What I remember being interesting was how the terrain and perhaps the units were 3D. Almost like "Total Annihilation". You might have played that RTS.
I hope I've explained enough to finally find this elusive game that haunts me to this day.
TL;DR This is not total annihilation. This is not dark colony. This is not command and conquer. This is not starcraft.