The "Dark Forest" theory posits that civilizations must preemptively destroy others to survive. However, the immense defensive advantages in intergalactic space make conquest economically irrational and nearly impossible. This suggests the universe will likely settle into a stable patchwork of isolated civilizations, not a state of constant war.
Principles of defense dominance only apply to technologically mature civilizations distributed across random orbits. Humanity, clustered on a single planet with a predictable orbit, is an easy target. The fact we haven't been attacked is strong evidence no hostile super-civilizations are nearby.
To counter devastating laser attacks on fixed targets like planets, a civilization's best strategy is to "starlift" material from stars and use it to power billions of mobile habitats on randomized orbits. This makes the civilization a diffuse, unpredictable "fog," rendering targeted bombardment ineffective and ensuring survival.
The energy needed for a defender to deflect an incoming "relativistic kill vehicle" (RKV) is vastly less than the energy an attacker must spend to launch it. This fundamental asymmetry makes large-scale conquest economically unviable, as the attacker expends far more resources than they could ever hope to gain.
Because mature, distributed civilizations are nearly impossible to dislodge due to defensive advantages, the long-term control of galaxies is determined by who colonizes them first. This brief "settlement phase" has permanent consequences, making the actions of nascent spacefaring species like humanity incredibly impactful.