The movie is not actually based on a true story. It was based on a story that was told by cowboys to writer Dennis Lynton Clark. The cowboys were working on his father's ranch in Montana during the 1940s.
The surplus cavalry horses were turned over to the Dept. of Agriculture and sold. They were never destroyed as in this film. In She Wore a Yellow Ribbon (1949), Harry Carey Jr. rode a horse named Soldier. Soldier was a former cavalry horse, probably sold at auction by the Dept. of Agriculture.
The names of the sergeants are the same as those used for the sergeants in Fort Apache (1948) except they are spelled differently. Some of the names were also used in other John Ford films. One of the sergeants in this film was named Quinlan; there is no sergeant named Quinlan in any John Ford film, but Ford did use the name "Quincannon" in several of his military-themed films.