This was discussed on TMC, which they said that Wayne had an old football injury for one, and that the Military believed his Movies would boost morale, and even had Wayne make some Military shorts (not movies), which TMC ran a few brief clips.. now if that was all bull I don’t know.. I choose to believe it, if you think it’s important to prove otherwise go do your own research.
Look at the Garry Wills’ book on Wayne. The studio wanted Wayne to stay home and he took the opportunity. John Ford, the director and his mentor, never forgave him for not enlisting and it became a sore point throughout both their lives. Ford was merciless on the subject and would take the opportunity to ridicule Wayne at nearly every opportunity.
If I need heroes, I’ll choose real ones.