Gifford is the executive officer of the USS Thunderfish, a submarine operating in the Pacific theater during the early years of World War II. The sub has been frustrated by the fact that too many of their torpedos hit targets but don't explode. Gifford and his captain, "Pop" Perry (Ward Bond), have been puzzling over the problem. During a re-supply stop at Pearl Harbor, Gifford finds that his estranged wife, a Navy nurse, has been stationed there. She's begun a relationship with Pop's younger brother Bob (Philip Carey), a Navy pilot. A later fight with a Japanese destroyer leaves the Thunderfish damaged, and during its refit Gifford finds himself facing the loss of his berth on the sub unless he can get a handle on the torpedo problem. He also finds himself again on the outs with Mary.
Operation Pacific came out in 1951, well into the era where Wayne was basically playing Wayne no matter what the character was named. He and O'Neal were supposed to have gotten along poorly, but both are professional enough to keep it off the screen. She is as snappy and witty as Wayne during the verbal sparring and creates a character just as real and just as solid an anchor for the story. Bond is his usual workmanlike self and Carey does well enough, but it's the well-sketched Wayne-O'Neal angle that sets Operation Pacific up as a high-level war movie with some weight.
Williams was canned from coaching because he cut corners in recruiting and promised players payments based on ticket sales, reasoning that they earned it since they were the ones doing the work (Although there was no NCAA at the time, the hypocrisy of schools and coaches benefiting from the work of players was alive and well). Under the rector's nose, he does the same thing here, but at first this leads to success on the field. That success puts pressure on his relationship with Carol, and Singleton begins to pressure him to allow her to have more contact with her mother. Even that gets complicated because of the budding chemistry between the coach and the social worker who is supposed to evaluate him and his family.
Reed, a year away from her Oscar for From Here to Eternity, gives depth and substance to her role as Wayne's antagonist. In an early scene, he dismisses her as a crusading dilettante with no understanding of the people she's supposed to work for, but is later surprised when she shows her real motivations and a history completely unlike his snap judgment. But the best foil for Wayne's dominating screen presence is Sherry Jackson as Carol. Jackson was no screen novice even at 11, and her ability to handle a scene and create a character was enhanced by Wayne's stepping back and giving her the room -- something he did quite often, despite that dominating screen presence.
Trouble was plagued with on-set disagreements between Wayne and first-time screenwriter Melville Shavelson, who at first agreed to allow Wayne's own script doctor polish dialogue off to better match the star's style but then had scenes without Wayne re-shot with original dialogue on days when Wayne was absent. One day he wasn't absent, learned of the re-shoots and disagreement blossomed. Despite the box-office power of Wayne and Reed, Trouble was one of Wayne's lowest-performing releases during his heyday. That's a shame, because it's one of the movies that put the star in a strong cast and in which he gave those other cast members room to work as well.