Conflict will increasingly be drone based. The controllers of those drones will increasingly be wielded by AI. This link is about tactics. This thread got derailed into strategy. But it’s reasonable to think that AI would do a good job of controlling attack air/sea drones with clear success criteria.
The standing armies are generally smaller than the ones before and after WW2, despite three times larger worldwide population. The effective mobilization potential of major countries is much smaller than before or after WW2 as many countries have moved on from total conscription where you'd expect most of adult men to have military training and a huge proportion of the population to actually fight in a war. The quantity of planes, bombs, guns and shells that we can muster is an order of magnitude smaller than 70 years ago, so while each bomb or gun is more effective, the total destructive power is less than it used to be. The world has 5 times less nuclear weapons as it used to have.
So the actual trend is towards a smaller scale of destruction. We have major wars that result in as much casualties as an average WW1 tuesday despite being as full-blown conflicts by the involved countries, mobilizing as much as they reasonably can in modern circumstances.
The Earth is too small and our weapons too powerful for playing child games anymore.
So it doesn't really make sense to train an AI for full scale conflict, nuclear arsenals are already MAD-sufficient enough. Instead, you'd have to model complex geopolitical, even cultural and psychological details to model surrenders and which territories one could lose, for example. Essentially AGI-complete tasks.
I know our realities are such that we can't let go of defense spending and defense systems yet, but it's looking increasingly ridiculous and dangerous to rely on military strength[1].
[1]: Instead of seeking ethical-economic-cultural multinational equilibrium, that is, a mutually acceptable plan toward individuals and development of our entire society/civilization.
In the sense of each "nation" (non-trivial political subdivisions in general) tolerating the collective vision for development of our society. I don't think bombs are a very effective form of communication or cultural-philosophical exchange.