It's also worth noting that WW2 by and large predates intermodal shipping containers. Apart from some experiments late in the war, the U.S. military did not use

It's also worth noting that WW2 by and large predates intermodal shipping containers. Apart from some experiments late in the war, the U.S. military did not use containerized shipping to any significant degree. Everything was shipped "break-bulk" which meant that every individual parcel had to be loaded/unloaded by hand every time it changed transportation mode. Also, the ships that carried these goods were tiny by modern standards. Every bit of extra volume and weight mattered much more than it does today.