Japanese Operational Idea (Scheme) for Sho-1 Operation, August 1944
Air Preparations
Preparations of naval and army air forces for defense of the Philippines were accelerated in the summer and early fall of 1944. The additional naval and army aircraft were redeployed to the archipelago, especially to Luzon. The construction of air bases was greatly speeded up.
Base Air Forces. On 1 September, the Fifth Base Air Force had about 410 aircraft in its inventories, but only about 250 were operational. Due to intensified work on repairing damaged aircraft, its effective strength was increased to 280 aircraft by the end of the first week of September. As of 16 September, the effective strength of the First Air Fleet fell to about 190 aircraft because of losses suffered from the Third Fleet carrier strikes. Just when the Fifth Base Air Force began to restore its combat strength, the enemy carrier aircraft struck the Manila area on 21 and 22 September. After 25 September, the number of aircraft increased, so that two weeks later the Fifth Base Air Force consisted of about 340 aircraft, of which some 200 were operational. The latter figure included 115 fighters and 21 carrier-type bombers. These fluctuations in overall strength and in the influx of fresh personnel were the main reasons that the Fifth Base Air Force was not fully trained by the time of the enemy landing at Leyte.
Vice Admiral Shigeru Fukudome was appointed the commander of the Second Air Fleet on 15 June 1944. He served in a series of high level planning positions between January 1940 and March 1944. He was known as an officer of great influence and ability. On 1 July, Fukudome was directed to concentrate his widely dispersed forces at Kyushu. Ten days later, he also moved his headquarters from near Tokyo to the Kanoya air base in southern Kyushu. On orders of the Combined Fleet HQ Fukudome was directed to redeploy a major part of his newly redesignated Sixth Base Air Force to Formosa and move his headquarters from Kanoya (southern Kyushu) to Takao, Taiwan. Commander, Seventh Base Air Forces was directed to make preparations to speedily move up first to southern Kyushu and then to Taiwan. CINC, China Sea Fleet would prepare for the movement of all his fighter aircraft to the Taiwan area as the situation might require.
The Sixth Base Air Force consisted of five major force elements. Western Attack Force One (W1AB), with headquarters at Kanoya, encompassed all tactical units based in southern Kyushu, with the exception of T-(aifu) Attack Force units. Western Attack Force Two (W2AB), with headquarters on Okinawa, included the land-based naval aircraft based in the Nansei Shoto. Western Attack Force Three (W3AB), with headquarters at Shinchiku, Taiwan, was under the command of the 21st Air Flotilla and encompassed land-based naval aircraft based on Taiwan. Western Attack Force Four (W4AB) was an administrative command, encompassing the Army Air Force units operating under the Commander, Sixth Base Air Force. The T-Attack Force was an air group specially trained for attacks in night and bad weather. It was composed of the more experienced crews of the various tactical units of the Sixth Base Air Force.
On 5 September, the Sixth Base Air Force received orders to attain combat readiness, in time to conduct the decisive battle outlined in the Sho plans. Its main task was to destroy enemy carriers. In addition, it would participate with other forces in destroying enemy fleet and landing forces specifically. Western Attack Force One, Two, and Three would attack enemy carrier groups, while Western Attack Force Four would attack transport convoys and an element of that force would attack carrier groups.
In late September, the Combined Fleet HQ directed that, as part of preparations for the Sho operation, the Base Air Forces should complete preparations for further redeployment by the first week of October. Specifically, the Sixth Base Air Force would deploy the 51st Air Flotilla (except for fighter aircraft) to the defense of Muroran (Hokkaido) and bases Kanto and Tokaido and place them under the command of the Seventh Base Air Force. Afterward, the Commander, Seventh Base Air Force would transfer the 702nd Attack Unit to the 51st Air Flotilla.
Fukudome served under Admiral Nobumasa Suetsugu, CINC, Combined Fleet, who put emphasis on rough seas training in the Japanese Navy in 1934. This was one of the reasons that Fukudome decided to create an elite force, T-Attack Force. Roughly, half of the T-Attack Force was composed of Army aircraft (two squadrons of heavy bombers). This was relatively new for the Army Air Force, which had organized its forces to fight the Soviet Army in Manchuria. The Army aircraft were short-range, and the heavy bombers were developed only after the start of war with China in 1937. By the time of the Air Battle off Formosa in mid-October, one of the squadrons had completed six months of training in bad weather conditions. The other squadron had by then completed only two months of training. Despite all that, the Army pilots were pretty bad at ship recognition, although the Navy pilots were not much better.
Army Air Forces. The Fourth Air Army was the principal army air force assigned to defense of the Philippines. It was commanded by Lieutenant General Kyoji Tominaga with headquarters in Manila. Tominaga was well known as General Tojo’s henchman. He served concurrently as deputy war minister and director of the all-powerful Personnel Affairs Bureau. After graduating from the Imperial War College in 1923, he had only three years of field duty. He was derided in Army circles as a petty bureaucrat. Reportedly, even the emperor was surprised by Tominaga’s appointment as the Fourth Air Army’s commander. He asked General Sugiyama Hajime, the new war minister, whether Tominaga knew anything about the Air Force; Sugiyama blandly responded that because Tominaga was in charge of the personnel bureau he knew Air Force organization.
The Fourth Air Army suffered large losses during the enemy carrier raids in September 1944. In addition, many of its senior officers had been debilitated by malaria or dengue fever. This, in turn, greatly hindered achieving a satisfactory degree of readiness. On 26 September, the Fourth Air Army consisted of about 400 aircraft, of which 240 were operational. Its strength remained essentially unchanged until 10 October. In mid-October the 30th Fighter Group was organized in Japan and then moved to the Philippines and was put under the control of the Fourth Air Army. In addition, the Manila Air Defense Command was established.
Air Defenses
The Japanese had in the Philippines a relatively well-developed system of air defenses of the territory. The Allied pre-invasion intelligence deduced the existence of seven air defense zones: Luzon, Bicol, the Visayas, Del Monte, Sulu, the Southern, and the Inner air defense zone, respectively. Each air defense zone encompassed all the airfields in the respective area.
Because of the growing importance of air defenses, the Japanese started in August 1944 to increase the number of air search radar stations in the Philippines. By the end of October, some two-dozen radar sites were built at the key island positions. The radars were installed in a great hurry and without being properly tested. Hence, many radars functioned improperly during intensive enemy carrier strikes in September and October 1944. Nevertheless, by November, the radars were improved so that they generally met operational demands.
As part of their preparations against enemy air strikes, the Japanese concentrated their AA batteries for the defense of the large metropolitan areas, harbors, bridges, airfields, stores, supply dumps, and fortifications. The heaviest concentrations of AA guns were on Luzon, Mindanao, and Cebu. The most heavily defended areas were Manila, the Clark Field complex, San Fernando (central Luzon), Cebu City (Cebu), and Davao.
For passive air defense, the Japanese extensively used dispersal, dummies, and camouflage. They had established an excellent system of dispersing their aircraft, allowing operations for an extended period. Sometimes entire flights of aircraft were located one to three miles from the field. However, the dispersals were often carried to extremes. Among other things, dispersal of the frontline air units increased the time necessary to put aircraft in the air, and in some cases, the use of long taxi-ways and rough landing strips contributed to the damage to planes’ landing gear. The most serious effect of the dispersal as practiced by the Japanese was the disorganization of ground services. In addition, bad communications between widely dispersed air units led to a breakdown of command and control. In contrast, dummies and camouflage proved to be highly effective. The Japanese skillfully used foliage and pattern painting in camouflaging their aircraft. In some cases, the Allied aircraft repeatedly strafed unserviceable enemy aircraft.
Air Searches
The Japanese planned for a relatively extensive air search effort in their preparation for the defense of the Philippines. These plans were prepared by the Combined Fleet and under Toyoda’s close personal supervision.104 Base Air Force commanders normally had the main responsibility for carrying out air searches in their respective areas of responsibility. Fukudome was formally responsible for conducting all air searches in the Taiwan–Nansei Shoto–southern Kyushu area. These searches were conducted from bases at Kanoya, southern Kyushu; Okinawa; and Shinchiku, northern Formosa and at distances of about 650 miles. It is unclear why Toyoda did not extend air searches beyond 650 miles, since the Japanese land-based attack aircraft and two-engine bombers had a maximum patrol radius of more than 800 miles.
Toyoda often unnecessarily interfered in the responsibilities and authority of his subordinate air commanders. He was very much in charge of all air searches in the Taiwan–Nansei Shoto–southern Kyushu area. Toyoda reportedly determined search sectors, and any changes in the search sector or pattern had to be reported to him. He went into such details as directing that search aircraft had to depart their bases between sunrise and two hours thereafter and fly at 1,500 feet altitude or less. He also determined the number of aircraft to be used for each search.
In the Philippines, the Commander, Fifth Base Force was responsible for long-range patrols (600–900 miles). Short-range patrols (300 miles) were conducted by an agreement between Commander, Fifth Base Air Force and CG, Fourth Air Army. Thus, no single commander was responsible for air reconnaissance in the Philippines area. In July 1944, the Navy and the Army authorized the respective subordinate commanders to reach agreements as to the division of responsibilities in the defense of the Philippines and its approaches.
Toyoda’s plan for air reconnaissance from Philippines bases contemplated searches up to 650 miles out from the bases in Manila, Davao, and Legaspi. Because of the U.S. Third Fleet strikes in September, long-range patrol planes in the southern Philippines were moved to bases to the west to provide better protection from the enemy’s future attacks. In late September or early October, the Navy-Army agreement provided for a more comprehensive air search plan. Naval search aircraft from Manila, Legaspi, and Zamboanga would conduct long-range searches. The Army aircraft from the bases on Luzon (Tuguegarao, Clark, Naga), Tacloban, and Davao would conduct short-range air searches.
Defense and Protection of Shipping
Protection of shipping was a critical element in Japanese preparations for the defense of the Philippines against an enemy invasion. This task was greatly complicated by the Allied submarines’ and land- and carrier-based aircraft’s successes against Japanese shipping. By the summer of 1944, sustained Allied attacks on Japanese shipping routes cut off the Home Islands from the Southern Resources Area. This led to a significant reduction of fuel reserves in the Home Islands. After the enemy capture of the Marianas, the shipping routes in the Philippine waters came under increased threat by enemy submarines, causing great delays in the transport of Japanese troops and materiel. Because of the lack of transports, the Japanese southbound troops and materiel began to pile up at Manila, the central distribution point for the entire southern area. Reportedly, personnel replacement depots in Manila were so overcrowded that local food supplies ran short and the troops had to be placed on reduced rations.
After August 1944, Japanese shipping losses soared. The enemy air attacks virtually shut down intra-island transportation in the Philippines. The Japanese were forced to carry essential war materiel on several transports to avoid the complete loss of materiel through the enemy sinking of a single transport. About 105,000 tons of general nonmilitary ships were made available to the Japanese Army for sending reinforcements to the Philippines. An additional 200,000 tons of shipping was transferred from general freight transport between Japan and China-Manchuria to the southern shipping routes. Some 232,000 GT of cargo ships was converted into oil tankers. At the same time, import of oil and critical raw materials from the Southern Resources Area was accelerated.
Heavy losses of merchant shipping from the enemy submarines forced the Japanese to make organizational changes to enhance the better utilization of available ships. A central coordinating body—Central Shipping Transportation HQ—for merchant shipping, composed of representatives of the ministries of war, navy, and transportation, was established in July 1944. The aim was to increase flexibility and reduce considerable waste in the use of available shipping. Under a new scheme, the ships that would normally return empty to ports in the Home Islands after discharging troops or supplies at Manila could be diverted to Singapore or some other port in the southern defense area and load critical cargo for the Home Islands. Likewise, nonmilitary freighters, hitherto sent out empty to southern ports, could carry military cargo as far as Manila.
The Japanese Navy also made several organizational changes aimed at increasing the effectiveness of defense and protection for merchant ship convoys. The General Escort Force HQ in Tokyo had the overall control of all convoy escorts in all the sea areas under Japanese control. Among its responsibilities was issuing general instructions regarding convoying. It also exercised authority over all convoy matters that were the responsibility of the naval stations. The number of escort ships was significantly increased. Most escorts operated on the southern route, under the 1st Escort Force, headquartered in Takao, Formosa. Four escort carriers, converted from merchant ships, were also made available for defense of convoys. Also, the new air groups, with radar-equipped aircraft, were used exclusively for patrolling shipping lanes.
In July, the Japanese started having groups of two or three escort ships accompanying their important convoys. Convoys carrying reinforcements to the Philippines were routed to Manila, and afterward troops and supplies were shipped to various destinations in the archipelago. The Commander, Southwest Area Force, controlled these operations. In July, four so-called “Coastal Defense Groups” were established to provide convoy protection in especially dangerous waters. By November 1944, the First Escort Squadron with headquarters at Takao consisted of four destroyers, 45 coastal defense ships, four minesweepers, two SCs, and one or two special gunboats converted from transports.
State of Defense Preparations on the Eve of the Enemy Landing
The Japanese started their preparations for the defense of the Philippines in early 1944. However, the need to defend a vast territory in the southern defense zone and insufficient forces on the ground and in the air complicated these efforts. By the time the Allies landed at Leyte it was estimated that only 50 to 60 percent of the planned preparations for ground defense had actually been carried out. Perhaps the most important reason for inadequate defense preparation in the Philippines in the fall of 1944 was the tremendous losses inflicted by the Allied submarines on Japanese shipping in the southern defense zone. Shipping traffic to the Philippines was reduced by half because of the actions of the Allied submarines. Expected troop reinforcements did not arrive, or if they did, their equipment was lost at sea.
Naval preparations for the defense of the Philippines focused on improvements of existing, and construction of new, naval and air bases. The focus was on the employment of forces for local sea defenses and special sea attack units. The Combined Fleet HQ did not intend to base its large surface ships and carriers in the Philippines. For the carriers, the need to train pilots required that they remain in the Inland Sea. Heavy surface forces had to be in the Singapore-Lingga area and northern Borneo because of the need for fuel supplies.
Air preparations for the defense of the archipelago were fragmented because the Army air forces and the Base Air Force did not effectively coordinate their plans. The Army-Navy central agreement was intended to improve cooperation between these two air services. However, in practice the cooperation between the Army air forces and the Base Air Force was inadequate. No joint command existed either for the offensive employment of air forces or for air defense of the archipelago. The Japanese Navy and the Army air forces made some efforts to provide timely warning of the impending Allied invasion of Leyte. However, insufficient numbers of search aircraft and the acute shortage of fuel made the task difficult for the Base Air Forces. This problem was more severe for the Army Air Force, because in addition to the lack of suitable platforms and fuel, the Army pilots were poorly trained for operating over the water.
