The Shō-Go Plan (Short for Shō-Itchi-Go, Operation Victory One) marked the last attempt of the combined Imperial Japanese Navy to defend its empire during the war in the Pacific. Japan’s strategy at the dawn of war in the Pacific had called for the occupation of all areas west of a perimeter extending to Marcus Island, Wake Island, and the Marshall and Gilbert Islands. Strong garrisons would defend these islands, and the imperial fleet would defend any threatened areas from its forward base at Truk. The Japanese hoped this defensive arrangement would make any invasion by the United States costly and force a compromise peace through war weariness. A critical requirement to the success of the Japanese strategy was an early decisive fleet action to destroy the U. S. fleet and negate the industrial superiority of the United States.
Events in the Pacific war soon dictated a change in this strategy. Japan’s failure to win the decisive battle at Midway (June 4-6, 1942) compromised its war plans and badly damaged its navy, particularly the carrier air arm. The campaign for the Solomons from August 1942 to the end of 1943 further weakened Japanese naval strength. Added to these setbacks were the late but devastating effects of the Allied submarine offensive against Japanese merchant shipping, particularly the loss of tanker tonnage that exacerbated Japan’s oil Shortages. Japan would lose 8 million tons of merchant shipping during the war, 60 percent of which was destroyed by submarines. Consequently, the Japanese navy in early 1944 had a striking distance of only 2,500 miles due to oil Shortages. The combination of these factors forced the Japanese to abandon their prewar strategy. The U. S. invasion of the Marshall Islands in late 1943 heralded this change with the withdrawal of the fleet from Truk to the Caroline Islands.
By mid-1944, the U. S. Pacific offensive had confined Japanese commerce to the areas behind an island screen consisting of the Philippines, Formosa, and the Ryukyu Islands. The Japanese war effort depended on the defense of this perimeter. The loss of any one of these islands would cut off the home islands from the oil resources of the southwest Pacific and starve the Japanese war machine.
Following the invasion of the Marianas (June 1944), the Japanese implemented a strategy to concentrate all military resources to counter a U. S. invasion of one of these vital strategic points. On July 26, 1944, the Naval General Staff informed the commander of the Japanese Combined Fleet, Admiral Soemu Toyoda, that the code name for these schemes was Shō, the character Shō meaning “to conquer.” From July 24 to August 1, the Naval General Staff created four Shō plans to deal with assaults on the vital island perimeter that guarded Japanese commerce: Shō-1 (Shō-Itchi- Go), for an invasion of the Philippines; Shō-2 (Shō-Ni-Go), for an attack on Formosa and the Ryukyu island chain; Shō-3 (Shō-San-Go), for defense of the home islands; and Shō-4 (Shō-Yan-Go), in case of an invasion of Hokkaido.
On March 1, 1944, the Japanese established the First Mobile Fleet, commanded by Vice Admiral Jisaburo Ozawa, as the means to execute these plans. It incorporated the Second Fleet under Vice Admiral Takeo Kurita containing the majority of battleships and cruisers of the Imperial navy. Its core consisted of the two most powerful battleships ever built, Yamato and Musashi (18.1-inch guns), and Nagato (16-inch guns). The First Mobile Fleet also incorporated the Third Fleet under Admiral Ozawa, which contained the carrier air strength of the task force. All light cruisers and destroyers not participating in antisubmarine duty supplemented these powerful sections of the fleet. In effect, Toyoda combined all remaining forces of the Japanese navy into one large strike fleet capable of concentrating on any area designated by the Shō plans. Each plan envisioned the use of land-based aircraft combined with carrier air forces to attack and decoy U. S. carrier groups as the surface forces destroyed U. S. warships and troop transports and supporting vessels for the amphibious assault. The Japanese hoped to employ their superiority in night fighting to crush the enemy, as they had done in the Battle of Savo Island (August 9, 1942), where they sank four Allied heavy cruisers and one destroyer at no cost to their own force.
The Shō operations were reactionary plans. The Japanese could implement none of them until they learned where the United States would next attack. U. S. strikes in the western Carolines at Yap and Palau, the occupation of Morotai on September 15, 1944, and especially subsequent bombings of the Philippines convinced the Japanese that the Philippines were the next target for amphibious assault. On September 21, Toyoda received a communiqué from Imperial Headquarters that it “anticipates carrying out the Shō operation sometime during or after the last part of October in the Philippines area.” It ordered Toyoda to prepare accordingly. On the same day that Toyoda received this communiqué, Japanese intelligence warned of an impending U. S. attack on Formosa to destroy Japanese bases north of the Philippines and isolate the islands. Toyoda reacted immediately and ordered an alert for the implementation of Shō-2, the defense of Formosa, and eventually amassed 600 carrier-based airplanes there at the expense of Ozawa’s carrier air force. The subsequent loss of no fewer than 650 planes during U. S. air attacks on Formosa (October 13-16) devastated the Japanese fleet air arm so recently and painfully rebuilt after the Battle of the Philippines Sea (June 19-21, 1944), a battle that had crippled Ozawa’s carrier-based air force. A further, and major, problem was the lack of time to train new pilots for service.
On October 17, Japanese coastal watchers east of Leyte Gulf spotted U. S. warships off Suluan Island. The following day Toyoda activated Shō-1 and ordered Kurita to sail the Combined Fleet from its base at Lingga Roads near Singapore to Brunei in Borneo. Toyoda gave Kurita operational command on Ozawa’s suggestion despite Kurita’s being a subordinate. Ozawa’s carrier force was in port in Japan taking on new carrier air groups and could not effectively command from such a distance. Ozawa was isolated from the rest of the First Mobile Fleet because the Japanese did not believe U. S. forces would attack the Philippines until November. Because the Japanese failed to concentrate their forces in time, the fleet had no chance of conducting operations as a unified force. On October 21, Toyoda ordered Kurita to sortie to the Tacloban area in the northwestern corner of Leyte Gulf. Once there, he was to destroy the U. S. surface fleet and then inflict as many losses as possible on the U. S. landing forces.
Kurita issued his battle plan for Shō-1 that night, ordering the main force to sortie from Brunei on the morning of October 22, to travel eastward through the San Bernardino Strait, and to arrive in the vicinity of Suluan Island in the early morning of October 25, X-Day, the scheduled day of attack. The main portion of Kurita s force, known as the First Diversion Attack Force (Center Force), consisted of super battleships Yamato and Musashi; older battleships Nagato, Kongo, and Haruna; twelve cruisers; and fifteen destroyers. The remaining portion of Kurita s command, under Vice Admiral Shoji Nishimura, consisted of old battleships Yamashiro and Fuso, supported by one heavy cruiser and four destroyers. Kurita ordered Nishimura to depart Brunei during the afternoon of October 22, sail through Surigao Strait, and meet him at the mouth of Leyte Gulf for a combined attack on U. S. forces on the morning of X-Day. Speed dictated the composition of Nishimura’s force (Southern Force). The top speed of aging Yamashiro and Fuso was only 21 knots. Kurita feared their inclusion in the First Diversion Attack Force would compromise the effectiveness of his force, the maximum speed of which without the two older battleships was 26 knots. His decision to detach Nishimura undermined the Shō-Go Plan by creating a weak task force ripe for destruction at the hands of superior U. S. forces. An additional force of two heavy cruisers, one light cruiser, and seven destroyers under the command of Vice Admiral Kiyohide Shima would sail from the Calamian Islands west of Mindoro and follow Nishimura’s force through Surigao Strait.
Japanese success depended on Admiral Ozawa’s carriers, the main force of the First Mobile Fleet. Ozawa possessed a formidable force on paper, his fleet consisting of carrier Zuikaku, three light carriers, two battleships, three light cruisers, and eight destroyers. However, his fleet was a paper shark. Because of heavy aircraft losses incurred in the defense of Formosa, most of the hangars on his carriers were empty. The combined air strength of all four carriers was only 116 planes, the pilots of which were woefully inexperienced. These weaknesses, combined with Ozawa’s force’s separation from Kurita’s force, led the Japanese to commit his carriers solely to a decoy mission. The main force of the First Mobile Fleet would sail south from Japan, maneuver east of Luzon, and bait the U. S. carrier forces away from Leyte to remove the threat of carrier-based air attacks on Kurita’s forces. All depended on the success of this decoy. The Shō-Go Plan also called for heavy reliance on land-based planes to protect Kurita’s warships as they approached and to attack U. S. naval forces, especially since Ozawa could no longer provide meaningful air support. The dependence on land-based air forces was a serious weakness in all the Shō plans but especially in Shō-1. The Japanese had in all only some three hundred fifty planes with ill-trained pilots based in Luzon. The Battle of Leyte Gulf clearly showed the uselessness of these planes: U. S. air strikes mauled the First Diversion Force (Center Force) with little opposition from Japanese warplanes. The condition of this land-based air force also undermined the Shō-Go Plan. The original plan, in which land-based air power played a critical role, was impossible given the strength of these forces.
The Shō-Go Plan had a number of flaws that made its success improbable. It was a complicated strategy that produced a lack of coordination of the many fleets. (Japan’s planners had a weakness for complicated operations that after 1941 never came off.) Nishimura’s Southern Force had a maximum speed of 21 knots, while Kurita’s force could steam at 26 knots. This difference made it difficult for the two forces to coordinate an attack. Nishimura’s force was also too weak to defend itself against the massive U. S. attack in Surigao Strait. Kurita’s dispersal of the forces at his disposal compromised the Shō-Go Plan from the start.
The Shō-Go Plan also had a more fundamental flaw. Ozawa’s First Mobile Fleet acted successfully as a decoy to give Kurita time to attack Leyte Gulf. However, even had the double envelopment of Kurita and Nishimura worked, the overall plan still would have failed. Once the U. S. carrier forces had destroyed Ozawa, they would have turned on Kurita, who had virtually no air cover. Undoubtedly the Americans would have then annihilated his fleet. Even if the Japanese had destroyed the U. S. force, the imperial navy would have paid a heavy price. The Japanese were prepared to accept such loss, however. The near success of this plan is important to remember. Kurita had the chance to destroy a portion of the U. S. fleet and landing force in the battle off Samar, but he lost heart and withdrew before he achieved a victory. Kurita abandoned the endeavor after sustaining heavy losses on his approach to the gulf and because he believed, incorrectly, that he faced a much stronger force than his own.
The failure of the Shō-Go Plan in the Battle of Leyte Gulf sounded the death knell for the Japanese war effort on two counts. First, it ensured U. S. success in cutting off the home islands from the rich oil resources of the South Pacific, consequently starving the Japanese war machine. Second, the Japanese after Leyte had no means with which to reverse their defeat in the Philippines. They lost all four carriers of Ozawa’s force, three battleships, six heavy and three light cruisers, and eleven destroyers. They also lost 500 aircraft and an estimated 10,500 sailors and airmen. The Shō-Go Plan was the last operation for the Imperial Japanese Navy as a coherent fighting force. It also marked the end of any Japanese chance of defending their empire.
FURTHER READINGS Andrieu d’Albas, Emmanuel Marie Auguste. Death of a Navy (1957). Dull, Paul S. A Battle History of the Imperial Japanese Navy, 1941-1945 (1978). Evans, David C., ed. The Japanese Navy in World War II (1986). Field, James A., Jr. The Japanese at Leyte Gulf The Shō Operation (1947). Jentschura, Hansgeorg, et al. Warships of the Imperial Japanese Navy, 1869-1945 (1977). Morison, Samuel Eliot. History of United States Naval Operations in World War II, vol. 12, Leyte (1975).
