Logistics is effectively the hardest problem and the most expensive one.

A lot of people don't realize that a lot of wasteful spending is effectively required in order to maintain any semblance or level of readiness.

If you are not manufacturing equipment, ammunition, and similar items then you have no one and nowhere to actually manufacture them. A large part of spending is keeping the people, skill sets, facilities, and supply chains running and operating at a minimum required level to support an increase in need. If you don't do this then when you need it, you can't manufacture it anymore, your entire supply chain has to start from scratch.

It's incredibly wasteful but also somewhat necessary.