I remember a wonderful game named "Millennium 2.2" on
the Atari ST. What I liked a lot about this game was
that you had to manage research, production,
extraction... without any war.
To be honest, once in a while, an attack from Mars was
announced, but with a few space fighters it was easy to
defeat them. The point is there was just enough action
to wake you up every few tens of minutes, but fight was
not a central point of the game.
Please do the game more economics than war.
BTW: very important also: the game was *very* easy to
understand and play.