Under Two Flags was the last of a series of films that Ronald Colman did for the newly formed 20th Century pictures which only lasted about two or three years before it merged with Fox to form that colossus of a studio that Darryl Zanuck ran. This film was in fact done under the banner of the new colossus.
Having starred in the silent version of Beau Geste, Colman certainly had the Foreign Legion credentials cinema wise. But Under Two Flags drags in spots the way Beau Geste never does. In fact the first half of the film deals with a romantic triangle between Legionaire sergeant Colman and the two women who love him, camp follower Claudette Colbert and British aristocrat Rosalind Russell. And there's Colman's commanding officer Victor McLaglen who is jealous over the fact that Colman has Colbert panting over him while she won't give McLaglen the time of day.
Another component of the Colman/McLaglen rivalry is that McLaglen is a professional soldier up from the ranks and Colman while a good sergeant is clearly upper crust. But back in those days one joined the Foreign Legion to get away from problems in civilian life wherever you came from. In fact where Under Two Flags is most similar to Beau Geste is why Colman joined the Legion. It's a plot device lifted from Beau Geste and one typical of those romantic days before World War I.
With Colbert and Russell in the film this will not be a male bonding adventure film. Russell as she did in her early films played aristocratic women of class. This was way before her gift for comedy was discovered and utilized. As for Colbert this film belongs more to her than anyone else. This was the most atypical part for her I've ever seen her do, but she does it superbly. Claudette was clearly poaching on Marlene Dietrich's territory as the camp following daughter of the legion that Marlene did so well in Morocco.
I don't think fans of romance and fans of adventure were completely satisfied with Under Two Flags. The genres didn't quite blend together successfully for a great film. Still Under Two Flags has its moments for everyone.