LinuxCon: Dragons and penguins in space

Without Satellites, military communications and targeting will suffer drastically.

On your own turf? Only if you've did something stupid and replaced reliable land-based communications with a sattelite-based ones.

the vast majority of the 'smart' bombs that are in use rely on GPS, without GPS we are back to Korea war era targeting precision.

Sure, but this an aggression, not defence. You may say that sometimes you actually need to attack someone and I may even agree with you but this does not change the fact that when you sent your 'smart' bombs to some other country you are an agressor.

communications would in some ways be in worse shape (while the military keeps some of the old stuff around, just in case, the difference between what they are trained to expect to have available, and what they would have available would cause problems in itself)

Again: not on your home turf.

space-based assets are a drastic force multiplier (both for offense and defense). I would say that they are well over a 10x multiplier, and I could see arguments putting them in the 100x range.

They are potent multiplier in a case of aggression, but for defence? Not so much. You don't need to use sattelites if you can just connect two military pieces with an optical canble (or just plan old radio). Yes, you can use sattelites to notice enemy earlier, but radars on ground work just fine, too. Only when you move to another, hostile country you need to rely on sattelites - and this move is act of aggression by defnition (when you move to friendly country you can bring the same on-ground network with you).