A System Agnostic Military SF Setting
Squaddies: The USE-Akurran War is a system agnostic setting and background for military science fiction RPGs. The accompanying series of Squaddies scenarios have deliberately had a certain amount of this setting pared out of them, so you can slot them into your own campaign setting. If however, you need a setting for your military science fiction RPG, then here is a guide to that universe, and to the second USE-Akurran war.
It is hard-ish science fiction - think bullets and body armour, not lasers and forcefields. The PCs will be assumed to be firing bullets, shells, missiles, grenades, calling on artillery support and hoping for air cover from craft which behave like shinier versions of modern military aircraft. Really big spaceships cannot land on planets – they sit in orbit and use shuttles or space elevators to get people and stuff to and from the ground.
The good guys and the bad guys are humans, not aliens. Planets with life on them (biosphere worlds) are rare and worth fighting over. Humanity has encountered a few intelligent alien species, but those have really only just got the hang of the Stone Age, so are no threat to mankind.