ODSTs can't be disregarded that's not how the UNSC military works or even the US military. Military's rely on different elements of branches to preform their duties in the battlefield to achieve victories. ODSTs are Marines too just a sub branch in the Marines Corps. It's no different than saying you can't include the UNSC Navy for support just ground on ground bare bones only no different than saying a 1v1. That isn't how it works but your question is based off the Spartans and its no argument that the Spartans were a crucial element to the UNSC's victory.
Battle for Alluvion (2542) - This outcome resulted in the planet being glassed however the Covenant were not able to gain any ground on the planet until the Covenant Support Fleet showed up and Glassed the planet. Marines and Army were only present.
Battle of Actium (2545) - UNSC Army Forces eliminated 3 of the largest Covenant staging areas in UNSC history. The planet was eventually glassed after this event.
Raid on Mount Haven (2552) - UNSC ODSTs destroy Forerunner artifacts prohibiting them from falling into Covenant Possession.
These battles resulted in the UNSC losing the planet by glassed or self inflicted destruction, no Spartans accounted for. So I am sure you will cite the fact these are considered Covenant Victories which you would be correct however these victories were done by nuclear bomb usage on themselves or glassed which also happened under Spartan support. I will say most of the battles won without Spartan support were based in the Navy which I didn't count because this is more based in regards to the ground combat rather then all battles without Spartans overall.
I will also add if a Spartan was on the planet I excluded that so even if a battle happened and a Spartan was on the planet but didn't take place in the battle I excluded it just so there isn't a call for technicality. The ones I cited are battles that made an impact on the war either threw moral/remembrance or strategic gain including asset denial.
You are correct though in a stand up fight bare bones or what have you, yes the Marines would loose but as I said earlier that isn't how the military works.
Overall though I think you and I agree on this topic. In more recent times its mainly Spartans in the fight since the Spartan IV Program and the deployment of the UNSC Infinity.
Yes they can. You said Marines, not Spartans and special forces.
Battle for Alluvion (2542)
The marines and Army had a substantial force, keeping a Covenant scouting attack bay for a few weeks. Later a support fleet arrived destroyed their support lines, and the colony soon fell to the Covenant shortly after. It was then Glassed after the fact.
Battle of Actium (2545)
And they only did so with the aid of a pair of HAVOK nukes and suffered extremely severe to total losses on the ground. 1 month later it was fully glassed after all resistance was gone.
Raid on Mount Haven (2552)
ODST's on a special mission, small scale.
I count 2 and both ended up being lost on the ground before glassing. Hardly countless and as I said, out liars that ended how almost all battles ended up. The UNSC lost on the ground and in space. They did better on the ground than they did in space but not better than the Covenant. Only the Spartans and small scale but overall significant, ODST incursions made any real difference.
I know the Marines don't loose all the time lol. That was never my point. Even Spartans got massacred at times too, particularly the 3's. They did have small victories here and there but always ended up tasting defeat. The ultimate goals of the Covenant were never hampered, barely even slowed at all.
I don't really count more recent times, since the Covies have collapsed and the rise of the Promethean's are the centre stage focus now.
Thank you for replying and showing examples though, I wasn't aware of either of them till now. :)
