I don't buy the argument about war being an instigator of progress at all.
1. Many of the advances people attribute to this are actually applications of previous scientific discoveries or technologies which came about independent of warfare, but war is kind of a big deal and builds stronger associations so that forever afterwards it becomes popular to identify those technologies as an extension of that conflict.
2. Even if I buy this argument, it's still a really weak one. If I focus tons of effort on one thing, I'm going to learn a bit about associated things, but not as much as if I had just focused on those associated things in the first place. Justifying the development of destructive technologies because it will indirectly lead to the development of constructive technologies is like saying we should become economists by studying chemistry because both require math skills.
3. You may argue that the motivation is what's really key, but this only belies our misallocation of resources. There are tons of people ready and willing to work on benefitting mankind, but they can't get the resources to pursue those goals unless they can prove themselves useful to powerful people who usually don't end up as such by being interested in helping others.
4. Tons of knowledge, progress, and potential is lost in conflict as history is re-written by victors, libraries and museums are destroyed, intelligent people and their works are assassinated or kidnapped or caught in crossfire, life in general is severely interrupted, resources are diverted into destruction, and those resources must again be diverted afterwards into rebuilding.
5. As military science advances, so does dystopian control of the populace. The military-industrial complex required to wage efficient warfare is also a hungry beast who doesn't just say "Ok I did my thing. Please return to your peaceful lives now."