Edit: Found: It's Fallen Haven.
Hello,
excuse me for using this forum to search for a non-Amiga game
The game as I remember it:
Release date probably around 1996 or 1997
Isometric sprite-based
Pre-rendered look like in Fallout 1+2
Looked very similar to Epic 40k: Final Liberation
SVGA resolution (probably 640x480)
A typical mission would have you land your dropship in an enemy city sector and move your troops around. Units were single vehicles or squads of soldiers.
Most missions took place in futuristic cities
There was also a campaign mode where you had a map with different sectors and you decided which ones to attack next.
Maybe someone remebers this game, I know that I played the demo back in the day
P.S. It was not W40k Chaos Gate