Here's an old post I made on the subject,
I foresee great developments and massive increase in the deployment of anti-materiel rounds (explosive, piercing etc. and even new EMP rounds), and interesting new war convention problems arising, especially if robots get mixed with infantry and follow it/replace it.
E.g. will robots be considered just materiel, like any other vehicle, even if they are capable of autonomous thinking?
Unlike a conventional vehicle or a drone, which is still operated by humans to some degree, a fully autonomous robot will raise some serious questions as to how much e.g. its programming abides by the Laws of War (Who will do the auditing? Who will guarantee that all nations using robots will use "conventional" rulesets? Will there be a common software framework for war droids?) and how it can handle certain situations like e.g. wounded enemy soldiers, not shooting on units bearing Red Cross symbols, recognizing surrendering units....and how it can avoid being fooled or distracted by enemies abusing those convention loopholes, if present. So, rather than fully autonomous, I foresee that military robots will primarily be remote-controlled and weaponized "walkers" or other relatively small vehicles for some time to come, tied to a human operator, just like K9 units.
A fully autonomous robot in the battefield would also pose some questions such as or whether it could be considered a lawful combatant (try sending a person to war without giving them a formal rank/position in the military, and see what happens to them should they ever get captured by the enemy). Who is it answerable to, in case of war crimes or abuses? Its unit's commander? Its programmers? Its manufacturer? Maybe they will be considered the same as K9 units (Police/Military dogs actually have a formal rank and function, and are considered Police Officers/Military Personnel to all effects and purposes), which are always paired to a human handler.
The very least, this is going to cause problems for mixed deployment of robotic/human troops, and interesting war convention problems. E.g. a force that lacks robots, will be allowed to equip regular troops primarily with anti-materiel rounds that are more effective at disabling robots but are banned against regular troops (e.g. explosive, piercing, etc.), if battling a force that has stated that it will/been proven that it does deploy robots as a primary infantry unit, rather than humans? Will the mainly robotized force have to use only conventional ammunition against human enemies?