USS Yorktown (CV-5) - Pacific Fleet

Pacific Fleet

Following Fleet Problem XX, Yorktown returned briefly to Hampton Roads before sailing for the Pacific on 20 April 1939. Transiting the Panama Canal a week later, Yorktown soon commenced a regular routine of operations with the Pacific Fleet. The Second World War started on 1 September 1939, but the USA was not yet involved. Operating out of San Diego, California into 1940, the carrier participated in Fleet Problem XXI that April. Yorktown was one of six ships to receive the new RCA CXAM RADAR in 1940.

Fleet Problem XXI - a two-part exercise - included some of the operations that would characterize future warfare in the Pacific. The first part of the exercise was devoted to training in making plans and estimates; in screening and scouting; in coordination of combatant units; and in employing fleet and standard dispositions. The second phase included training in convoy protection, the seizure of advanced bases, and, ultimately, the decisive engagement between the opposing fleets. The last pre-war exercise of its type, Fleet Problem XXI contained two exercises (comparatively minor at the time) where air operations played a major role. Fleet Joint Air Exercise 114A prophetically pointed out the need to coordinate Army and Navy defense plans for the Hawaiian Islands, and Fleet Exercise 114 proved that aircraft could be used for high altitude tracking of surface forces - a significant role for planes that would be fully realized in the war to come.

With the retention of the Fleet in Hawaiian waters after the conclusion of Fleet Problem XXI, Yorktown operated in the Pacific off the west coast of the United States and in Hawaiian waters until the following spring, when the success of German U-boats preying upon British shipping in the Atlantic required a shift of American naval strength. Thus, to reinforce the U.S. Atlantic Fleet, the Navy transferred a substantial force from the Pacific including Yorktown, Battleship Division Three (the New Mexico class battleships), three light cruisers, and 12 accompanying destroyers.