Operation Pacific is a 1951 World War II submarine film starring John Wayne and Patricia Neal, featuring Ward Bond and Philip Carey and directed by George Waggner. The technical advisor for this film was Admiral Charles A. Lockwood, the actual Commander, Submarine Forces, Pacific (COMSUBPAC) during World War II.
During World War II, an American submarine, the Thunderfish, under the command of Cmdr. John T. “Pop” Perry (Ward Bond), takes on a group of children and nuns to transport them to Pearl Harbor. including a newborn infant nicknamed “Butch”. The sub sights a Japanese aircraft carrier and attacks, but its torpedoes malfunction, exploding halfway to the target. Pursued by the carrier’s escorts, the sub manages to escape.
While in Pearl Harbor, the ship’s Executive Officer, Lt Cmdr. Duke E. Gifford (John Wayne) goes to visit Butch at the base hospital, and runs into his ex-wife, Mary Stuart (Patricia Neal), a Navy nurse, and they kiss passionately. Unfortunately, Mary is now romantically involved with Navy pilot Lt. (j.g.) Bob Perry (Philip Carey), Pop’s younger brother. Duke pursues Mary anyway, but is sent to sea again before anything is settled.
As the sub returns from the patrol, they spot a Japanese freighter, but, again, their torpedoes fail to explode. The enemy ship raises the white flag, and the Thunderfish surfaces and approaches it. The freighter turns out to be a Q-ship that opens fire on the American sub. Mortally wounded, Captain Perry orders the boat to dive, knowing that he will not be able to get below before she does. With the sub now under Duke’s command, the freighter is rammed and sunk. The Thunderfish, with her bow damaged as a result of ramming the Q-ship, limps home to Pearl Harbor.
Back at Pearl, Bob Perry believes that the order Duke gave to dive the boat killed his brother, and won’t listen to Duke’s explanation. Mary tries to comfort Duke, but he rejects her attempts.
Working with the base’s torpedo specialists, Duke and the crew of the Thunderfish undertake an investigation to find out why their torpedoes are not exploding. When they finally discover the answer, Duke goes to Mary to celebrate, but she rejects him: since he wouldn’t let her into his life when he was at his lowest, she feels that they cannot have a real relationship. Her superior, Cmdr. Steele (Kathryn Givney) overhears the conversation and castigates Mary for throwing away her chance for happiness with Duke.
Once again, the Thunderfish heads out to sea, and finds a Japanese fleet heading for Leyte. Even though it will reveal their position to the enemy, the sub broadcasts the fleet’s position. Once Pearl Harbor acknowledges receipt of the message, Duke salvoes all his torpedoes and runs for it, throwing the attacking Japanese ships into chaos. Though she has been knocked about by Japanese depth charges, the sub manages to sink a damaged Japanese aircraft carrier.
In the next phase of the battle American carrier planes arrive to attack the Japanese fleet. The Thunderfish, now assigned to lifeguard duty, helps to rescue shot down American flyers, and does so while under attack from Japanese planes. While rescuing Lt. Bob Perry, the Chief of the Boat, and Junior, a seaman from a Navy family, are killed and Duke is wounded by a strafing Japanese fighter.
When the Thunderfish returns to Pearl Harbor after this patrol, Mary is waiting for Duke. The two, reconciled, head to the hospital, intending to adopt Butch.