I often think that the acting of Ronald Reagan is unfairly maligned. While he was far from a great actor, he was very nice in many films--playing an excellent "everyman". However, Reagan himself must take some of the blame for his reputation, as the films he chose to perform in were often quite limp--particularly at the end of his career. Often, he seemed to take any part and didn't seem to follow up on his successes. For example, at the same time he made THE VOICE OF THE TURTLE and JOHN LOVES MARY (both wonderful films), he also made THAT HAGEN GIRL (among the entries in Harry Medved's book "The Fifty Worst Films of All Time").
Now early in his career, Reagan also was relegated to some dreadful B-films but at least with most of these you can't blame him. He was not yet a star and simply had to take what the studio gave him. Despite despising his Brass Bancroft films (and they were bad), he had no choice but to take them as he was a lowly bit actor until his breakout films, such as KINGS ROW.
Considering that SERGEANT MURPHY was only Reagan's third film and his first starring film, you can certainly understand his acting with a horse! Yes, I did say horse! It seems that 'Sergeant Murphy' is actually the name of a horse and Ronnie is devoted to it in a rather strange and unnatural way (not THAT unnatural--get your mind out of the gutter). When his father sold the horse to the military, Reagan joined the army just to be near the Sergeant!! I don't know about you, but I'd just find another horse! However, this is a Hollywood B-film and naturally by the time it's over (just 57 minutes later), Ron not only has gotten the girl but Sergeant Murphy is world-famous and a champion--all in under one hour!
There is nothing particularly bad about the film but sadly there is absolutely nothing good about the film other than Reagan's surprisingly good performance. He was an avid horseman in real life and served with the cavalry, so he was able to make this ludicrous film seem convincing to a degree I wouldn't have thought possible. However, it's still a pretty dumb film and not even for a millisecond is the plot believable or even particularly interesting.