Let me preface this by saying I've already finished the piece this question is about *but* I'm wondering if I missed something in my logic so I want to see if there's something you see that I didn't. The basic question is for what tangible, material reason or reasons (so not matters of philosophy or just "how evil can we be today?"), would a star system, that isn't doing badly and isn't overcrowded, invade another star system that is no better than their own? The system they attack has the same number of habitable worlds, same survey numbers on quality, and quantity of raw materials, same standing population. Especially is there a reason to attack a system that isn't better than yours in such a way as to risk the habitability of it's only terrestrial world?