Take something as simple as boots. In war, soldiers are usually doing a lot of walking and good boots prevent many injuries and improve effectivity of troops. So suddenly you decide to send millions of conscripts into war. Sadly you have outsourced the boots manufacturing industry to the country you are waging war with. Had the industry been in your country, you could have told them to retrofit their lines to manufacture your boots, but sadly all the knowledge, together with the population that is used to the repetitive nature of factory work is in a different country now.
Remember how much struggle there was distributing even simple things like masks and PPE during the COVID pandemic?
Of course you can solve the boots problem, but you'll have the same variant of problem for a lot of things. Solving all these problems all at once is an insurmountable task.
Even building a single Photolitography plant takes hundreds of millions of USD and years from start of planning to conclusion, with the involvement of a large number of companies from around the globe, each specialized to their own part of the process, and world leader in that part. So where will you manufacture your chips needed for your autonomous robot army?
Remember how much struggle there was distributing even simple things like masks and PPE during the COVID pandemic?
Of course you can solve the boots problem, but you'll have the same variant of problem for a lot of things. Solving all these problems all at once is an insurmountable task.
Even building a single Photolitography plant takes hundreds of millions of USD and years from start of planning to conclusion, with the involvement of a large number of companies from around the globe, each specialized to their own part of the process, and world leader in that part. So where will you manufacture your chips needed for your autonomous robot army?