How about Space: above and beyond? Despite the hokey sounding title it was an aswome series about a group of U.S. space marines fighting in a losing war against an alien race that was decimating human colonies and threatening earth itself. This was all taking place less than a generation after an A.I. war where humans had just barely survived a rebellion by artificial intelligence droids they'd created as servants. The A.I war had already reduced the human population to the point they started making genetically engineered humans called in-vitros which were now suffering discrimination from the rest of the human population as the war with the aliens (called the chigs) started.
The pilot episode actually showed them going through basic training with none other than R. Lee Ermey playing the drill seargeant. The backstory to this thing was so well thought out and intricate, it really put this show in a class by itself. It was awsome, and ended on a cliffhanger, but was never renewed for a second season (I hate it when that happens).
I remember that show! It was as good as you describe, very well thought out. Reminded me of a 'thinking man's' Starship Troopers
. It was done by Chris Carter, the same person who brought us the X-Files
, and Millenimum
(if you remember that one - another excellent show.)