How the allies would have won the war without John Wayne to fight all the battles I can't imagine! Operation Pacific is pretty run-of-the-mill stuff as WWII films go. It is the story of a US submarine, USS Thunderfish, on patrol in the Pacific, at first with Ward Bond as skipper and Wayne as executive officer. Plus, there is a love triangle complication for Wayne with Patricia Neal back in Pearl Harbor. The only point of historical interest is the quest to resolve the US Navy's unserviceable torpedoes, which was a problem for a couple of years. It is also good to see the writers and actors making fun of themselves and Hollywood in an amusing scene when the crew is watching another Hollywood submarine film, Destination Tokyo, with Cary Grant.
All in all there's not much to say for or against the film. Black and white seems to suit the style of the film. The plot is pretty predictable, with the submarine sailing missions and having problems with its torpedoes. Back on shore Wayne is trying to make up with his ex-wife, but there's a new man on the scene - someone he already knows. And all of the strands are brought together pretty much as one would expect. It is a perfectly pleasant and enjoyable way to spend an hour or two, but it's never in danger of straying into classic territory. However, for the price at the time of writing it's quite a bargain.