The short version containing some of my understanding: Things in space are far away and expensive to reach in a timely way. So, if someone gets to some resources first, they can spend a small fraction on defenses and be reasonably well defended unless an attacker spends far more resources sending over things to attack them.
One major counterargument is that maybe the most efficient space megastructures will be soft targets (because they can’t jitter fast enough) meaning that defense is effectively very expensive because you can’t use the most efficient megastructures.
Whether you can cause various destructive chain reactions is pretty important. If locusts could benefit from causing vacuum collapse, or could trigger star supernova, or could efficiently collapse various bodies into black holes, that could easily eat up large fractions of the universe.
What makes you think that that space combat is significantly more likely to be defence dominant?
The short version containing some of my understanding: Things in space are far away and expensive to reach in a timely way. So, if someone gets to some resources first, they can spend a small fraction on defenses and be reasonably well defended unless an attacker spends far more resources sending over things to attack them.
One major counterargument is that maybe the most efficient space megastructures will be soft targets (because they can’t jitter fast enough) meaning that defense is effectively very expensive because you can’t use the most efficient megastructures.
Whether you can cause various destructive chain reactions is pretty important. If locusts could benefit from causing vacuum collapse, or could trigger star supernova, or could efficiently collapse various bodies into black holes, that could easily eat up large fractions of the universe.