Space Warfare Seems Mostly Defense Dominant - By Beren Millidge

TL;DR

• 1

  Defense wins once civilizations get paranoid: Millidge's core claim is that equally capable Kardashev III civilizations spend far less mass and energy defending than attackers spend trying to destroy them across intergalactic distances.

• 2

  Intergalactic lasers are terrifying but mostly punish fixed targets: A galaxy-wide phased array could concentrate about 10^35 W onto a target a few hundred kilometers across and vaporize Earth in 10 microseconds, but aiming data is roughly 5 million years stale between Andromeda and the Milky Way.

• 3

  Relativistic kill vehicles are better for hunting movers, but still deflectable: RKVs can retarget using onboard sensors as they approach, yet defenders only need tiny nudges, sensor blinding, or surface ablation from defensive lasers to send them into empty space.

• 4

  Classic invasion fleets look worse than sci-fi suggests: Ships that need to decelerate advertise themselves for thousands of years with huge exhaust signatures, carry brutal rocket-equation costs, and arrive against defenders with local industry and short supply lines.

• 5

  The winning defensive posture is diffuse, redundant, and weirdly inconspicuous: Instead of clustering around Dyson spheres or the galactic core, a paranoid K3 spreads hydrogen via star lifting into billions of mobile habitats on irregular orbits, making the galaxy look like a uniform mesh of waste heat.

• 6

  The far-future implication is a partitioned universe, not endless conquest: Once a mature civilization secures a galaxy, Millidge expects it to be very hard to dislodge, so wars should be rare, expensive, and mostly matter during early colonization races.