Over 16 million served.
There were more than 2 million draftees.
Not everyone in uniform was enthusiastic. I would love to believe that was the case. The draftees did their duty, so it isn’t a slam. But the truth is different than the John Wayne movies.
From the National WWII museum:
Once the U.S. entered WWII, draft terms extended through the duration of the fighting. By the end of the war in 1945, 50 million men between eighteen and forty-five had registered for the draft and 10 million had been inducted in the military.