The friendly infantry that you're trying to protect are going to love having friendly flak shells exploding fifteen feet above their lines, to say nothing of t

The friendly infantry that you're trying to protect are going to love having friendly flak shells exploding fifteen feet above their lines, to say nothing of the fact that drones are so maneuverable that swarms will attack from every reachable direction simultaneously. Flak shells will be minimally useful (and ultimately more expensive than the drones that do get shot down; you've already lost economically). And "radar can detect birds, so it can detect drones" means nothing whatsoever unless you're willing to waste all your AA ammo depopulating the pigeon population. Again, nobody is saying there's no defense, but autonomous drone swarms are going to be as important to warfare as the airplane (which, likewise, there are defenses against). The important thing is to have planners acknowledge it.