What was the Japanese plan for the defense of the Philippines and why did it not work?
Any major naval operation or maritime campaign contains a number of elements that collectively ensures the accomplishment of its objectives. An overall operational design should exist to provide that one's own forces and assets are employed in a coherent manner. Its principal elements are guidance, objective, desired end state, identification of the enemy's critical factors, and an operational idea or scheme.
The Japanese hoped to achieve several objectives in their first major operation in defense of the Philippines. Their principal strategic objective was to defeat the U.S. forces landing at Leyte and thereby halt the Americans' advance across the Pacific. Forcing the U.S. juggernaut to shift to strategic defense would allow the Japanese to strengthen their own defenses and reconstitute their forces. They also hoped that by inflicting a humiliating defeat at Leyte Gulf, they would force the United States and its allies to reconsider overall strategy in the Pacific and perhaps abandon the policy of accepting nothing less than Japan's unconditional surrender. In retrospect, the Japanese strategic objective was too ambitious, because there was little, if any, hope that the United States would change its strategy. Realistically, the Japanese only would have been able to slow the operational momentum of U.S. forces in their drive toward the Japanese home islands—even if their plan had been executed flawlessly.
The Japanese operational objective was to destroy U.S. transports and thereby break up the amphibious landing. They expected to lose more than 50% of Admiral Takeo Kurita's force, in order to destroy 50% of the U.S. ships in Leyte Gulf. Japanese planners, however, did not consider an alternative operational objective in case U.S. forces completed the landing before the arrival of Japanese forces.
An important task of the operational commander is to identify the enemy's critical factors, which include all his strengths and weaknesses. The "critical strengths" are the enemy capabilities needed for the accomplishment of his objective. The most important of them is the center of gravity, often found where mass is concentrated most densely. This is the reverse of "critical vulnerabilities," critical weaknesses that facilitate attack on the enemy's center of gravity.
In the Philippines, the Japanese selected the wrong operational center of gravity: U.S. transports in Leyte Gulf instead of carrier task forces. Yet their choice was a logical consequence of their inability to inflict serious damage or neutralize the U.S. carriers, given the battered state of their own naval aviation. They did, however, find an innovative way to neutralize the threat posed by the U.S. Third Fleet—by using Vice Admiral Jisaburo Ozawa's carrier force (main body) in a feint to draw U.S. carriers northward. With the enemy's operational center of gravity so neutralized, Japanese planners hoped to obtain additional leverage by destroying amphibious shipping and ultimately weakening the enemy's strategic center of gravity—the U.S. will to fight. By destroying the ships in Leyte Gulf, the Japanese would seriously reduce U.S. amphibious lift capability and thereby slow down considerably the operational momentum of the U.S. offensive across the Pacific Ocean.
At first glance, the Japanese operational idea behind this Sho-1 plan was simple. But, in fact, it proved too complicated. It envisioned a double envelopment in the south, while the northern pincer was an operational feint. Five different task forces. from Borneo, the Ryukyus, the Philippines, and the Inland Sea were to advance toward the Philippines, in a converging line of operations. The basic intent was to maneuver a formidable First Diversionary Attack Force, including the world's two largest 62,300-ton Yamato-class super-dreadnoughts armed with nine 18.1-inch long-range guns, into position to attack and destroy U.S. transports, supply ships, and close-support units in Leyte Gulf. The Japanese expected that the U.S. Navy would use its surface fleet to prevent Vice Admiral Kurita's force from reaching the transports in the gulf.
Because of the lack of an effective carrier force, the Japanese planned the employment of land-based air to support the actions of surface forces moving from a widely separated base of operations toward Philippine waters. Land-based air was ideally suited to attack the approaching U.S. invasion force, and air bases in the Philippines occupied a central position. The Japanese aircraft attacking enemy ships or troops on the ground would be operating along short, interior lines.
Because of the weakness of their carrier force, the Japanese planned to use the gunnery strength of their heavy surface ships in combination with land-based air to inflict high losses on the U.S. invasion forces. The sector of main effort was in the waters around Mindoro. The Japanese selected as the point of main attack the Tacloban anchorage in Leyte Gulf.
In planning a major naval operation, the Japanese invariably included an elaborate deception scheme, and the Sho-1 was no exception. The success of Kurita's massive force of firepower depended on deceiving U.S. operational commanders about the true objective. Therefore, the Japanese drew an elaborate operational deception plan, with Ozawa's force as the centerpiece. The latter was to assist in the penetration of the First Diversionary Attack Force by diverting U.S. heavy carriers to the northeast of Luzon, and subsequently to join the other forces by attacking the "flank of the enemy task force." Japanese operational planners put considerable emphasis on studying psychological traits of the opposing commanders. Hence, they had high hopes in the success of their deception plan because of Admiral William H. Halsey's well-known propensity to act rashly and aggressively. The Japanese also planned extensive use of dummy radio messages to deceive U.S. forces.
Japanese planners apparently paid scant attention to a vitally important task—protecting one's own operational center of gravity. By the fall of 1944 it was clear to the Japanese (but apparently not to Halsey) that because of the small number of aircraft available and especially poor state of pilots' training, Ozawa's carrier force did not represent an operational center of gravity; rather, heavy surface forces under Admiral Kurita would have been such a center and all efforts should have been made to protect that force, as it advanced from Brunei through the confined waters of the Philippine Archipelago on its way to Leyte Gulf via San Bernardino Strait. No provision was made, however, to provide reliable, continuous air cover for Kurita or other surface forces operating in the Philippines area, allegedly because of the shortage in fighter aircraft. Moreover, Kurita neither asked nor expected support from army land-based aircraft. Land-based aircraft were not to be used to coordinate attacks with carrier-based air operating east of Luzon. These examples show how poor the interservice cooperation was for this critically important major joint operation.
The Japanese operational scheme called for the entire operation to be executed in four phases.
- The combined First and Second Base Air Fleets were to attack U.S. fleets at ranges of at least 700 miles from the Philippines. Army land-based aircraft were to coordinate their attacks with land-based naval aircraft in destroying the remaining U.S. forces at the landing beaches.
- The First Diversionary Attack Force was to sail from Brunei Bay, Borneo, to intercept U.S. convoys and support ships and conduct surface engagements.
- If a U.S. amphibious landing took place, Kurita's force was to attack the invasion point and destroy amphibious landing forces.
- The main body, then deployed in the Inland Sea, was to be used as a feint to lure the U.S. carrier task force toward the north and away from the expected amphibious landing area, and thereby allow Kurita's force to accomplish its mission.
The Japanese drew up a meticulous timetable for their five fleet elements taking part in the operation. Their movements were synchronized with respect to objectives, place, and time. Such a rigidly laid timetable, however, was difficult to follow in practice, even under the best of circumstances. No provision was made for timing the movements of surface forces. For example, it was clear, even without the benefit of hindsight, that any threat or actual attack by U.S. submarines and carrier-based aircraft would force Japanese ships to conduct avoidance maneuvering, resulting in delays measured in hours.
In planning operation Sho-1, the Japanese committed all available forces and assets. They decided to sacrifice the entire effective strength of the Combined Fleet to protect surface lines of communication between the home islands and the resource-rich southern area of their empire.
Operational sustainment of surface forces and aviation assigned to execute the Sho-1 plan was quite inadequate. In contrast to the U.S. Navy, the Combined Fleet never fully developed an underway-replenishment capability. Two groups of supply ships were assigned to the First Diversionary Attack Force: the 1st Supply Force, with eight tankers and two coastal defense ships, was deployed in the Singapore-Brunei area; the 2nd Supply Force, with five tankers and a single coastal defense ship, was deployed at Sam-Urucan and Singapore-Bako. Only one tanker (then based· at Sana, Hainan Island), however, was capable of refueling at sea. The main body's supply group was not established until 18 October and consisted of only two tankers screened with one destroyer and three escorts. This group was ordered the same day to proceed to Tekuyama, and then to remain on standby at Amami O Shima. The shortage of fuel severely restricted speed of the Japanese surface ships during deployment, in combat, and withdrawal from their respective areas of operation.
The Sho-1 plan was bold and risky, but too complex to achieve its stated objectives. Its success depended heavily on adhering strictly to the timetable, achieving operational surprise and deception, and—above all—effective air cover for the fleet forces. The latter was probably the most decisive factor in the Japanese defeat. Regardless of its size and firepower, a surface fleet without effective air support has little or no chance of success in the face of enemy land-based air.
The Sho-1 is an example of what happens when cooperation among services is poor or nonexistent. It makes a powerful case that jointness is critically important for the success of a major naval operation or maritime campaign. It also shows that a failure to ensure smooth coordination among naval combat arms can be fatal for the success of the operation..
The Sho-1 plan was highly unrealistic, because there was a clear disconnect between objectives to be accomplished and forces and assets available at the strategic and operational levels. The planners also failed to strike a balance between offense and defense in the employment of their own forces and assets. Although air cover for the fleet forces was of utmost importance for success, adequate forces were not assigned and effective coordination between the land-based air and the fleet forces was neither planned nor effected. A shortage of escorts also precluded the planners from providing effective antisubmarine warfare for surface forces. The lesson here is that no navy should ever neglect any aspect of naval warfare, whether it is protection of maritime trade, antisubmarine warfare, mine warfare, or air defense. Such inattention in peacetime invariably affects force planning, the quality of officers assigned to less-glamorous, but highly important warfare areas, and the quality of training. Ultimately, these mistakes are costly, because deficiencies in adequacy of forces and assets and training cannot be corrected easily—if at all—during war.
A plan for a major naval operation or maritime campaign never should count on errors and mistakes by the opponent—and above all should not bank on miracles, which rarely happen. The plan should be clear, simple, and above all flexible. It should realistically anticipate possible enemy reaction and unforeseen events, and remain flexible.
Any plan must provide an alternate objective. A contingency plan must be drawn up, in case the primary objective changes or cannot be attained. Higher headquarters should assign to subordinate commanders minimum—not maximum—objectives. It should make clear, however, that any additional objective achieved will be highly welcome and will exploited by other friendly forces. The operation plan must be changed-partially or completely—if the situation at hand changes significantly. For this, the operational commander must conduct a running estimate of the situation.
A plan of a major naval operation should provide for flexibility in the synchronization of forces and assets. Ideally, the synchronization schedule should be focused on the objectives to be attained, not on certain timelines to be followed. One's own forces should not be dispersed beyond mutually supporting distance, unless each possesses overwhelming strength against any combination of enemy forces that might appear.
The 50-year-old Sho-1 plan shows the critical importance of unity of command for the success of a joint naval operation. It is always much better to achieve unity of effort through unity of command than through informal cooperation. A good plan also should state clearly the lines of operational and tactical control for subordinate forces. Once an operation starts or is in progress, command-and-control responsibilities should not be changed unless an extraordinary event forces the reallocation or reassignment of forces and assets.
Fast, reliable, and secure theater-wide communications are vital for the success of a major naval operation. Otherwise, the result is excessive operational security, which in turn almost invariably affects cooperation, which in turn complicates the chances for success in combat. Operational reconnaissance and intelligence should be established firmly in peacetime.
The lack of adequate operational logistics and sustainment severely restricts the planners' options in designing a major naval operation or campaign. It also adversely affects the choice of lines of operations, speed of advance, and even the organizational options.
Dr. Vego is an instructor at the Naval War College, Newport, Rhode Island. He served as a second mate on board West German merchant ships.