We never knew it was a war when it started. We didn't even know when it started. It was a war the same way that cleaning out your gutters, or degaussing a CRT monitor was a war. (Forgive that these examples are anachronistic: I am translating, of course). On our end, at least. For them it was like deodorizing a room. We weren't aware of each other's presence, we were shadows slipping by each other. There weren't governments, either, at least not galaxy wide for us or them. The Milky Way, for some reason of panspermia or prevailing conditions, had developed life and civilizations made out of matter. A fairly obvious choice, so obvious that we did not think about it. When carbon chain organisms met silicoids, that was the largest difference we can imagine. And when we all started moving across our galaxy, and moving into the Magellanic Clouds, we were surprised to find them uninhabited by sentient life: it seems like nothing more than pond scum grew in the planet across the clouds, from the near-frozen planets circling red dwarfs in the periphery to the irradiated metallic planets near the blue giants in its heart. At that point, we were really beyond governments, and even species, just groups of life going from the center to the periphery. But we started noticing discrepancies: our planets and settlements and Dyson Spheres were afflicted by the oddest types of very long wavelength electromagnetic radiation. And so, we cleaned it away, targeting areas that were emitting radiation with magnetic monopole treatment and later black hole generators. We had a lot of technology, and we didn't think of it as military, we just thought of it as environmental management. And while we were doing this, more environmental anomalies occured: low frequency radiation, neutrino cascades, and sudden explosions of quarks from seemingly empty space. This went on for thousands and tens of thousands of years, without us knowing what it was: two forms of life trying to commit genocide, never realizing that there was sentience on the other side of the strange phenomena. And thus, genocide, planets blown apart because they were in the way of flow lines of radiation and even more exotic energy, magnetically charged clouds dispersed because they were interfering with life on planets and ships. Increasingly stronger measures taken over what both sides just thought of as storms. Firefighters are heroes, only working to rescue life, but the firefighters on both sides destroyed entire civilization.
For whatever reason, the galactic halo is full of what we would call dark matter. And this includes the Magellanic Clouds, seemingly only satellites of our own galaxy, but full of this other type of matter that we hardly understood. We knew about dark matter, could detect it and know how it interacted, but we could only see parts of it. And of course, for them, we were the "dark matter", but even less important since there was less of us than there was of them. We lived in parallel, our two universes only interacting weakly with each other, and that interaction being observed, on both sides, as exotic anomalies that needed to be cleansed. And so they were.
I watched all of this, an organic-robotic computer, the imprint of a living mind in a Radiothermalgenerator powered drone, scouting out near what turned out to be a dark matter cluster when it was hit, unexpectedly, by a black hole generator. The little ball of ice I was on was sent flying at incredible speeds by the gravitational whiplash, and ever since then, I have been flying out from beyond the Milky Way and the Clouds, viewing the flashes of light and destruction across the spectrum. And flying further out into the cold, into the emptiness, only receiving thousands of years later the explanation to what had happened, broadcast on all wavelength. And this war, this genocide, this destruction, will be the only thing to think on as I fly further into the dark, waiting for my power source to gradually go away. And I try to think, whether all the crimes we were committed, were crimes if we did not even know there was someone on the other end of the bullets we were firing. And that single thought, and the view of the receding galaxy, are the only things I have on my little ball of ice as I fly out into the emptiness of intergalactic space.