Quote Originally Posted by Jayngfet View Post
It really comes down to who wins in space.

In the novels it's mentioned that Spartan II's in the very earliest non-shielded armor were able to consistently beat the covenant on the ground, even if they did take a lot of casualties to the point of only having one active member by the very first game.

However, they still lost because the covenant would just blow the entire planet to hell from orbit and that would be the end of that conflict.
See the difference between the UNSC and the Imperium, is that if the Imperium start losing on the ground, they do the same thing. Their ships execute Exterminatus or Virusbomb the planet and destroy every living thing on the surface. The Imperials also have planetary defenses to stop other factions from doing exactly the same thing, so just imagine how different the war in Halo would have gone if the UNSC had ships and defense systems to deal with that.