Not My War

What is the harvester doing so deep in the forest? A battle happened here. I need to track it down and see what happened.
I wonder who sent them here and why...

Haven't I warned you against ruining our Forest, aliens?
All-Mother trusted you, but you just went on with your nasty deeds? You're going to die. We're going to destroy all your disgusting metal monsters and wipe out your homes, build without permission on the land of Eden!