The Japanese may also need F35B’s to be able to disperse their assets in case the Norks (or anybody else) succeeds in taking out their major air bases. The entire VSTOL/STOVL concept (that eventually evolved into the Harrier) was a German post-war concept. Drawing on their WW2 experience and what a Soviet invasion would look like the Germans assumed they’d have no airfields after the first 48 hrs.
How do the F35’s stand up to the Chinese J Series?