It's a comment about the other piece: Trade and specialization. It's more efficient to have specialized countries. If Germany and Japan focus on optics, that's

It's a comment about the other piece: Trade and specialization. It's more efficient to have specialized countries. If Germany and Japan focus on optics, that's more efficient than having an optics industry in each country. Everyone is wealthier. It's also more brittle; if WWII breaks out again (as a hypothetical), the allies don't have access to optics, and can't repair step-and-repeats. That, in turn, means they can't manufacture ICs. And so on, down the line.