re: Greyhound question for Navy folks - no real spoilers

Rank was a lot harder to get back in those days. The army post ww1 was very small. I'm not saying the movie is realistic, but for instance. George S Patton entered the Army in 1909 as a second lieutenant of Cavalry. He wasn't promoted to colonel until 1938. Almost 30 years later, and I expect that was because of WW2 looming on the horizon. He was a Major from 1920 until 1934.