USS Missouri was the only battleship of the United States Navy not to be placed in reserve status prior to the outbreak of the Korean War. In fact, President Truman personally intervened to keep the battleship in commission due to a fondness for the ship (it was christened by his daughter, he was from Missouri, and it was where Japan formally surrendered). Then on January 17, 1950, Missouri ran aground near Hampton Roads while on a training exercise. It was refloated February 1 and repaired in time for service in Korea, but if things had gone differently repairs might have been more complicated.
What if Missouri had been placed in mothballs or more damaged in its 1950 grounding incident and rendered unavailable for service when the Korean War broke out? How long would it take for other battleships to be brought back into service for naval operations? Would heavy cruisers be able to pick up the slack? How might amphibious warfare doctrine change?