Now that you mention it... We may first infer intelligent extra-terrestrial life exists from imprints left on planetary/stellar motion. We could theoretically find an entire star system in total disarray for millions of years after a galactic-scale genocide. Haha, imagine seeing an accretion disk, or newly congealed planets, around a 4 billion year old star. The most realistic space combat (I'd certainly like to think) is none at all. Morals and ethics seem to evolve with technology, and once a civilization reaches the threshold of interstellar capabilities, they should be pretty Zen by then. But maybe that's just the closet optimist in me speaking. P.S. Never give AGI your actual personal information, they have an aggressive sales department.
Footfall by Larry Niven and Jerry Pournelle starts with a prologue at JPL, where scientists are observing a "braided" ring around Saturn that is later revealed to be caused by the ion drive of the Fifthp mothership as it emerges from its hiding place. Heinlein's Stranger in a Strange Land mentions the Martians' destruction of the "fifth planet" because of the disharmonious nature of its inhabitants, leading to what we know as the asteroid belt.
