Wayne has orders to guard a wagon carrying O'Brien's family to meet a stage coach. This provides further complications in the (apparently) long-running love triangle between O'Brien's daughter, cutie Joanne Dru, and two hot-blooded young lieutenants, John Agar and Harry Carey Jr. The coolest soldier appears to be Ben Johnson, but he's only a sergeant, and thus of little interest to Dru. In fact, since Carey is only a 2nd lieutenant, Dru gives him the time of day primarily because it makes full lieutenant Agar predictably jealous.
How I felt about it. She Wore a Yellow Ribbon is, of course, the middle film in John Ford's so-called 'Cavalry Trilogy.' All three films star John Wayne, and offer a Ford/Wayne favorite, the comical, burly, and hard-drinking Victor McLaglen, in a supporting role. As in the first film, Fort Apache, John Agar is the love interest, but this time he isn't courting Shirley Temple, but her understudy, Joanne Dru.
Dru has received much criticism over the years simply for not being an A-list actress despite key supporting roles in two A-list westerns, this one and my personal favorite, Red River. But if she's good enough for Ford, she's good enough for me, and if she isn't quite pretty enough for you, remember that pickings were likely slim for marriageable young women on a remote western fort in 1876, especially if it's important that she be the daughter of the commanding officer. It must be important to Agar, particularly since he was after real-life wife Shirley Temple in the last movie, who was playing the daughter of top brass Henry Fonda.
How others will see it. For me, the plots of the cavalry trio movies run together shortly after one or another has receded from immediate viewing. It's been a while since I've seen Rio Grande, and all I can remember about it is that it must be the one with Maureen O'Hara in it, since she wasn't in the present film and I don't think she was in Fort Apache.
For you, the (presumably) dedicated disciple of John Wayne westerns, the film may be more distinctive. Certainly, it is a good film, and nearly a very good film. It is odd, though, that for all the soldiers and braves criss-crossing the Utah desert, the body count is very low, especially on the Indian side. One suspects that the Cavalry mercilessly slaughtered tens of thousands of Indians during the 1870s, as depicted in Little Big Man. Ford's rendition of western history is more chivalric, and thus more appealing. And less accurate.