I think the radar problem was "in general, therefore we cannot use this gun"
Drones aren't robots, but remote controlled aircraft. They can do anything an aircraft designed in a similar manner with a human pilot can do, but with a delay that comes from waiting on a signal. A Jammable signal. This means a 13 year old kid playing videogames is training to be a foot soldier in the next war. Wars will be fought between drone armies trying to get to control centers, and then by drone armies trying to spread jammers. Humans will still come into play to destroy jamming sites, until we start with reliable quantum communications or something equally unjamable. I expect as time goes on and human casualties in war to go down, there will probably be laws of war that outlaw killing of humans at all. And then people will throw that out the window like all other laws of warfare. Toxic Biochemical spraying drones because they can't find the peope operating the opposition soldiers...
Space warfare will be fun. We can drop rocks out of range of ground-based weapons, so the bigger and easily seen stuff would be worthless. Small, insurgant-friendly weapons is what a ground force can expect to see. This means we are accomplishing NPR's mission of preparing for alien invasion, by training crops of insurgants all around the world.
The problem is, if the aliens don't see value in us greater than the cost to pacify an insurgancy, it's cheap and easy to make us, and all life on earth, extinct.
(EDIT:Forgot to talk about railguns.
A railgun works by accelerating a slug through the miracle of magnatism. There is recoil, but thanks to the difference between friction, and the fact we are talking about constant acceleration instead of burst acceleration from an explosive one-off compound, it's not going to be as noticable. Recoil of a firearm is all from acceleration in a fraction of a second. Spread it out over a little time and it's easy to deal with.
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