The difference is in "active"/intelligent versus "passive"/dumb targetting that's performed by the machine.

The missile, once fired, has the general vicinity (if not the exact position) of the target and is armed by the operator. Therefore, the operator is fully accountable for the targetting. Same goes for the landmines, once placed. Hitting civilians is reckless at best, and negligent at worst.

An autonomous weapon system (AWS) usually means that the system, once deployed, can do the targetting itself over any arbitrarily bounded location. An AWS can continue finding targets as long as its hardware allows it. For kamikaze drones, it's one time; for other drones, the ammunition & battery are the limits.

We currently rely on human targetting because we assume that A) humans are able to distinguish between legitimate and illegitimate targets "well-enough", and if not, B) at least we can hold them accountable (e.g., punish them for war crimes).

An AWS provides a layer of plausible deniability: the operator can claim that the system wasn't developed well enough, while the developer can claim that it wasn't used as intended. Given the inscrutability of modern computational intelligence - i.e., visual-action neural networks - this could potentially lead to very worrying incidents.

From a technical POV, the difference between a manually operated drone and an AWS drone may not be massive. From a military POV, it's just another legal lethal tool in the arsenal.

But from a social/civilian POV, the use of AWS is still 'not normal' and opens a can of worms. Targetting while evading counterattacks and crimes successfully is a bottleneck for manual operation. That's no longer the case with AWS: build 20 thousand drones, for example, and you can trivially win by overwhelming any manual defense of frontlines or cities. And knowing the history of human warfare, winning can range from relatively bloodless regime changes to utter destruction of the loser's civilization.

So, the best outcome is similar to nuclear deterrence or MAD: as long as everyone has 20 thousand AWS drones, they're safe.

> Same goes for the landmines, once placed.

Landmines can be dropped from the air by the thousands and many land mines can survive for decades. Placing a landmine anywhere is essentially the same as firing a bullet blindly through time. And no individual soldier has ever been held accountable for a landmine that killed a civilian years down the road.

Which doesn’t make what you said about drones any less awful. Just that landmines are already uniquely awful.