Station HYPO

Did the Imperial Japanese Navy use a mock raid on Pearl Harbor that was conducted on February 7, 1932 as a blue print for their December 7, 1941 attack?
On February 7, 1932, a mock raid was staged on Pearl Harbor, as part of a military exercise designed to test Pearl Harbor’s vulnerability to a surprise attack. In the period between the Washington Naval Conference in 1921, and 1940, the U.S. did not have a two-ocean navy. The main Pacific anchorages were in San Diego and San Francisco where the fleet could be deployed quickly in the defense of the Panama Canal or of the Hawaiian Islands. Its proximity to the canal also allowed for its rapid transfer to the Atlantic should it be needed there.

“Planners” at the War Department had been considering the possibility of war with Japan since at least 1906. The eventual strategy, dubbed War Plan Orange, anticipated that in the event of a war with Japan, the Philippines and American bases in the western Pacific would be either blockaded or overrun. In the interim, the U.S. Pacific Fleet would concentrate its strength along the West Coast until the ships had received their full complement of crew. During the 1930s, ships operated with only half of their allotted crew as an economy measure. Once the fleet had been readied, it would sail west to relieve the Philippines. With the Philippines secured, the fleet would proceed to blockade Japan and seek a decisive naval showdown with the Japanese fleet.

This strategy was consistent with the writings of American naval strategist Alfred Thayer Mahan who argued that future wars would be settled by decisive naval engagements. This view was widely shared among the world’s naval powers, including Japan. Given the critical role of Hawaii in a Pacific campaign, the idea of beefing up U.S. Naval forces at Pearl Harbor was not new. It had been discussed since at least the end of World War I.

Since 1923, the U.S. Navy had conducted large-scale naval exercises, termed “Fleet Problems,” during which U.S. Naval forces would engage in mock battles with a purported European or Asian attacker. Fleet Problem Number 13 was a mock attack by a “militaristic, Asian, island nation against the military base at Pearl Harbor.” The exercise was designed to test Pearl’s defenses and assess its vulnerability to an attack.

The attacking force was under the command of Rear Admiral Harry Yarnell. The admiral was a qualified naval aviator, one of the few admirals to have earned his aviator wings at a time when battleship command was still the path to promotions. In 1927, he took command of the aircraft carrier Saratoga and was instrumental in developing carrier tactics. At the time, carriers were classified as “fleet scouting elements.” They were not valued as capital ships and were considered expendable.

Yarnell maintained that Japan “had always started operations by attacking before a declaration of war.” Accordingly, he designed an attack plan that utilized carrier aviation to launch a surprise attack on Pearl Harbor. Pearl’s defenders had anticipated that Yarnell would attack with his battleships. Instead, he left his battleships behind and advanced with the carriers Saratoga and Lexington to a point north-northeast of Hawaii. At dawn, on Sunday February 7, 1932, Yarnell launched his attack with a force of 152 planes from the two carriers. His attack force first attacked the airfields and then proceeded to attack the ships along battleship row.

Yarnell achieved total surprise. The airfields were put out of commission, with not a single plane getting airborne during the attack. The attacking force scored multiple hits; they dropped sacks of white flour to simulate bombs, on the battleships. The umpires declared that Yarnell’s attack had been a complete success and declared him the winner. The Army and Navy brass, however, would have none of it. They complained that Yarnell had cheated. He had attacked at dawn on a Sunday morning, a time considered “inappropriate” for an attack. His attack vector from the north-northeast had mimicked planes arriving from the mainland. Most importantly, the Navy argued, low level precision bombing of battleships at anchor was unrealistic since “everyone knew that Asians lacked sufficient hand-eye coordination to engage in that kind of precision bombing.”

Pressured by the War Department, the umpires reversed their decision and declared that the defenders had won the exercise. The Navy and its “battleship admirals” ignored Yarnell’s contention that Pearl Harbor was vulnerable to an attack by naval air power. The exercise was widely reported in the press and was observed by Japanese naval officers at the Japanese consulate on Oahu. Some 10 years later, the Japanese Navy would launch an almost carbon copy attack on Pearl Harbor, utilizing six carriers and double the air power used by Yarnell.

The only significant innovation employed by the Japanese Navy was the use of air-launched torpedoes against the ships in Pearl lagoon. A year earlier, the Royal Navy had used slow Swordfish torpedo planes to attack the Italian fleet at its base in Taranto. The success of that attack was not lost on Tokyo. The U.S. Navy had dismissed its relevance to Pearl because Taranto’s harbor was around 75-feet deep, almost double the depth of Pearl Harbor, and it did not believe that air launched torpedoes would work in shallow waters. The Japanese Navy solved that problem by modifying their torpedoes to give them a flatter glide path.

The definitive story of the attack on Pearl Harbor has not yet been written. Pearl still has secrets to disclose. What is not a secret, however, is the fact that the Japanese attack plan against Pearl Harbor had been designed a decade earlier by an American admiral.

Source: military.com Joseph V. Micallef