Other posters complained that in Soldiers Three Granger imitates Cary Grant in Gunga Din. I'm a fan of Gunga Din but hadn't really thought of comparing the actors as I watched Soldiers Three. Instead I found myself admiring, and frequently amused by, Granger's comic abilities--of which he showed flashes in other movies but of course he was better known as a romantic swashbuckler or, later, a western hero comfortable with the ladies.
Another complaint is that the film is a Hollywood potboiler, but what's surprising is how much British comic style survives in this production from the West Coast of North America. The comic pace may seem "lazy," but it's familiar even now in the Brit-coms that play Saturday nights on PBS. Granger's timing and interplay with Sykes and Cusack are admittedly unspectacular but nonetheless well-practiced in technique and pleasantly warm with human feeling.
As a final recommendation, the story, characters, and dialogue may be closer to authentic Kipling than Gunga Din, whose screenplay was a free expansion of a not-very-long poem that contributes little to the film with the same title. Long ago I read Kipling's Plain Tales from the Hills partly about English servicemen in India and introducing the characters of Soldiers Three. I think there were later stories collected under the title Soldiers Three. Anyway the plain and humane style remind me of those early stories by Kipling, which gambol between stereotypes and humanity. Kipling's Anglo-Indian writings benefit from his youth and early journalistic career primarily in what is now Pakistan. The film of Soldiers Three seems true to this author's spirit.