I did learn one interesting little tidbit while stationed at Schofield Barracks, HI a couple years ago. Right across from Schofield is what is now known as Wheeler Army Airfield. During WWII, the US started to build an underground factory right next to Schofield and the air field. This bombproof factory would be an area where they’d conduct final assembly of fighters. These fighters would roll off the line, make a hundred yard journey to Wheeler, and then fly out to a carrier deck or if necessary straight into the battle of Hawaii.
This undertaking was originally started during the early months of the US of the war when everyone feared that Japan would soon invade the islands. The underground factory wasn’t completed until several years later and by that point Japan didn’t have a navy left, so it was never used for it’s intended purpose. At various points it’s been mothballed, used as a storage facility, or for other purposes and still exists to this day.