The Duke or The Draft Dodger?
The most balanced article I found. It leaves whether Wayne or the studio was responsible as unknown.
https://www.warhistoryonline.com/instant-articles/john-wayne-the-duke.html
At first, Wayne was exempted from military service due to his family status and his age. He was 34 at the time and had a wife and four kids to support.
Several other stars, however, joined the ranks despite having a family to support. Henry Fonda, Gene Autry, Jimmy Stewart, Clark Gable, and Robert Montgomery had all enlisted themselves in spite of having similar circumstances to that of Wayne.
Ronald Reagan, who had also recently got his breakthrough movie King’s Row in 1942, joined the service for the military signal corps, declining several potentially big movies. Many fellow celebrities voluntarily enlisted themselves. As a result, it didn’t take long for Wayne to become the center of controversy.
Despite being close friends who remained deeply connected for almost their entire careers, a sore point was always there between Wayne and Ford due to Wayne’s failure to serve in the military. He also got into several fights with servicemen during the war because of his alleged “draft dodging.”
Since Wayne’s death, there has been an extensive debate on whether his absence from the war was justified or whether he was just a draft dodging hypocrite. We can probably never know for sure what kept him from joining the ranks. This knowledge is something he took with him to his grave.