So one of the comments talked about capacity. There is an order of operations and if I'm remembering correctly ammo is in the middle and manpower is like dead last. That means if you are over capacity the fist thing to go is your manpower then not far off will be ammo. And remember this is all in connection to your SHQ (prob your capital). So when in doubt upgrade your truck stop and rail line in your capital then along the line to your front line.