Thoughts on planetary combat

[Samuel]

Because you can always swamp the defenses with asteroids. Unless the system has had all debris cleared out, and all the solid worlds are bristling with guns.

[Formless]

But, Sam, if you're proposing a civilization where space travel is ubiquitous enough to allow for interplanetary warfare in the first place then its quite possible that could be the case (at least for the major core worlds certainly). The asteroid belt doesn't need to be completely cleared out, just enough that the nearest continent sized behemoth is several months away, all the weapons grade asteroids have been located and tagged by ground based telescopes so there's no surprises, you can't just inundate the defenses with natural projectiles, *edit* and whatever is left has ships and defenses of its own to deal with */edit*. If you're doing any serious asteroid mining you might just fulfill those criteria without even meaning to, given enough time.

The defense system need not be impenetrable, it only needs to make such an attack infeasible to pull off or just too damn expensive in terms of time, resources, or sheer effort for the attacker. You can always say "LOL, we'll just swamp the defenses," but in practical terms when you're a fleet commander for a warring nation and you're under a deadline to conquer the planet before political backlash or disenchantment on the home front sets in, you very well might decide its not worth it and move on.

Besides, every time the "we'll just overwhelm the defenses with sheer numbers or brute force" argument is made, what you're really doing is tacitly conceding that the defenses are worth the cost of installation. If you have to resort to overwhelming force just to take the planet, then the defenses are doing what they were intended to do; making the attackers job every bit as hellishly difficult as possible.

[Samuel]

But, Sam, if you're proposing a civilization where space travel is ubiquitous enough to allow for interplanetary warfare in the first place then its quite possible that could be the case (at least for the major core worlds certainly). The asteroid belt doesn't need to be completely cleared out, just enough that the nearest continent sized behemoth is several months away, all the weapons grade asteroids have been located and tagged by ground based telescopes so there's no surprises, you can't just inundate the defenses with natural projectiles, *edit* and whatever is left has ships and defenses of its own to deal with */edit*.

Well if you cover every single rock and body in the system with guns than of course the invaders wouldn't be able to use them without reducing them first. Of course if you have hyperdrive and tractor beams you can just pop behind a moon and start flinging it at them, but in a case where everything in the system is fortified you are going to have to attack them one by one. If static defenses are cheap enough compared to ships it would be feasible and the attacker would have to spend time burning out the shields for outlying posts before they could get to the juicy center.

Of course given the vastness of space you might be able to move on in and ignore the outer posts but you'd probably need to destroy them so you can use their mass to bombard the enemy.

Of course if this is a system where the planets are all very close to the Sun (either one of those close in gas giants with habitable moons or something designed) things get more complicated.

The defense system need not be impenetrable, it only needs to make such an attack infeasible to pull off or just too damn expensive in terms of time, resources, or sheer effort for the attacker.

So essentially it makes for a universe where the results of war hang on entirely fleet actions because attacking planets is a waste of ships when your enemy still has ships and can oppose you?

[Simon_Jester]

That's not unprecedented; Age of Sail naval warfare tended to work that way. Ships lacked the firepower to crack fixed defenses casually, so even an utterly dominant fleet generally didn't accomplish much except to deny the seas to the enemy really thoroughly. In the long run that won wars, but not in the short run.