Maybe one day war will be less about killing people, and more of a battle between countries' best engineers.
Maybe I'm just optimistic, but I think robot wars would be a hell of a lot better than real wars.
When two robots fight each other, it's not because the other robot is the target, it's because it's an obstacle between them and the human targets that will actually affect the war.
That is of course assuming that the most efficient strategy to achieve a surrender doesn't actually end up being a bypass of enemy AI and direct targeting of human populations. This would only be possible if there's a huge mismatch between offensive and defensive capability. But then you end up with a MAD situation similar to what we have with nukes.
That said, I expect that the flip-side is that this tech would ultimately make a guerilla war by a local population against an occupying force very very ugly for the guerillas.
So it boils down not to robots killing robots, but robots killing humans, while other robots try to stop them.
(That said I'm less optimistic I guess.)