The impact of cutting a military budget worldwide to half of today's spending would bring up to 8% percent.
If we still need to have wars worldwide, why not take a look at the current China India conflict as an example. There they agreed to fight only with sticks and clubs, and it's working great for both sides.
But that's the beauty of the Military Industrial Complex. It's not about war(s). It's about enriching the few at the top of the MIC food chain.
In theory, I agree with you. The reality is, we'll likely be seeing the MIC(s) be enlarged. The argument will be that more power and more force are necessary as resources become limited, "interests" need to be maintained, etc.
It’s a drop in the bucket compared to the other changes we need.
Of course we can do things in parallel, and I’m not saying this isn’t worth doing, but this is one of the least important things we could do to curb emissions.