I don't get the story. So, the planet is infested and a team is sent to stop it and is assumed to be all dead. Then they send a battalion armed with nuclear devices obviously meant to be used. It seems that somehow for some reason that would not be logical to link to the aliens one of the ships gets massively damaged and crashes into what clearly no one would survive but somehow people do. There are clearly still ships in space from the communication of "is anyone else DOWN there with you"
So I assume the player is one of the unfortunate to crash down because of a reason that likely will never be explained or satisfying. Why not just send down drop-ships (they would no doubt have to have such being so advanced) set up a LZ and pick up as much as they can, and then just nuke the planet from space? We have the tech today to nuke from space so this wouldn't be a problem. Ignoring the fact of the seemingly impossible to survive crash there doesn't seem to be any logical reason why one would have to remain on the planet for any length of time. Land, rescue, nuke.
They have communications, advanced technology, what would it take 10 minutes? If that?