From various documentaries and articles, I've gathered a few things about future non-existential but still catastrophic risks from military AI.
It may increase the likelihood/frequency of war crimes:
In the initial stages, AI drones / autonomous weapons may frequently misidentify targets.
AI drones / autonomous weapons may be programmed to not be capable of refusing orders from human or AI commanders to commit war crimes.
To achieve objectives, AI commanders may choose highly bizarre and unconventional solutions that involve committing war crimes, due to not having a complete intuitive human morality, like Yudkowsky's unsafe genies.
Human commanders that already want to commit war crimes may feel emboldened, that they can avoid personal blame, or that they can convince moderates, if an 'objective' AI advisor calculates that committing war crimes is the optimum strategy to achieve objectives.
Generative AI misinformation may become so effective and widespread that there is an impenetrable smokescreen of plausible deniability of war crimes ever being committed.
AI powered research may continue to discover vast numbers of new chemical and biological weapons.
It may increase the severity of war crimes:
AI drones/commanders/advisors may reach the point of universal significant outperformance of their human counterparts.
Due to the above point, they may become effectively impossible to defend against by non-AI forces, committing the intended war crimes faster and to a greater completion than would normally be practical.
Also due to the same point, if at any point an AI decides on the specific war crime of torture, it may vastly transcend the known limits of suffering.
On the other hand, AI armies would probably look pretty badass, so I'm sure it cancels out :)