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Kuroshio no natsu: Saigo no shin'yō tokkō (Kuroshio summer: Last shin'yō special attack)
by Eidai Hayashi
Kōjinsha, 2009, 277 pages

Emperor Hirohito announced the surrender of Japan by radio message at noon on August 15, 1945. At about 7 p.m. on the following day, several huge explosions at the Navy's shin'yō explosive motorboat base in Yasu Town (now part of Kōnan City) of Kōchi Prefecture killed 111 men (including 23 shin'yō crewmen) in the 128th Shin'yō Special Attack Squadron and wounded many others. The book Kuroshio no natsu: Saigo no shin' tokkō (Kuroshio summer: Last shin'yō special attack), published in 2009 more than 60 years after the event, investigates in detail the following questions: Why did the accident occur at Yasu? What was the source of a report that the enemy fleet was heading north toward the Japanese main island of Shikoku? Why did the young shin'yō boat crewmen prepare to sortie? This historical study on a little known incident delves deeply to find the answers to these questions, but ultimately many uncertainties remain about what exactly happened and what led up to the accident.

The author Eidai Hayashi interviews many Shin'yō Special Attack Corps survivors and other accident eyewitnesses in his search for answers to what happened at Tei Base in Yasu Town. The interviewees include several Japanese Navy veterans who served at shin'yō bases other than Tei Base. He also consulted numerous written sources in his research as evidenced by about 50 works listed in the bibliography. Hayashi has authored many books related to Japan's wars and former colonies such as Taiwan and Korea, and he is the recipient of several literary awards. His prior publications include two well-researched books about Japan's tokkōtai (Special Attack Forces): Jūbaku tokkō sakuradan ki (Heavy bomber Sakura-dan special attack plane) (2005) and Rikugun tokkō shinbu ryō: Seikansha no shūyō shisetsu (Army special attack Shinbu barracks: Detention facility for survivors) (2007).

The author in the beginning does not clearly lay out either the book's purpose and scope or the methods he used to obtain information, but the book cover gives the main questions he tries to answer in the book. However, even despite these main questions, some parts of the book seem to have little relationship with the explosions at Tei Base that killed 111 men. However, most of these parts not related to Tei Base will appeal to someone interested in Japan's Shin'yō Corps as Hayashi covers details of other shin'yō bases located in Kōchi Prefecture.

A two-page insert in front has historical photos of the plywood shin'yō boat, which had a one-man Model 1 and a two-man Model 5. The shin'yō boat was powered by a truck engine, and it carried 250 kg of explosives in its bow. The boats were suicide (special attack) weapons in which crewmen lost their lives as the boats exploded when hitting enemy ships. The book includes over 30 other photos of shin'yō squadron members, current locations of the shin'yō bases, and other subjects.

Toyoji Kunita, former 128th Shin'yō Squadron member who received serious injuries from fire at Tei Base in Yasu Town. Author Eidai Hayashi could not interview Kunita since he had passed away before the start of the research.


The book's contents are organized clearly into six chapters with each chapter divided into several parts. After an Introduction that gives a background on shin'yō bases in Kōchi Prefecture and a summary of the accidental explosions at Tei Base in Yasu Town on August 16, 1945, Chapter 1 presents the shin'yō special attack weapon and general background on shin'yō crewmen. Almost all crewmen received their training at Kawatana Torpedo Boat Training School in Nagasaki Prefecture. The young men selected to become shin'yō crewmen were almost all aspiring aircraft crewmen of 17 and 18 years of age in the Navy's Yokaren (Preparatory Flight Training Program) at Tsuchiura Air Base and Mie Air Base.

Chapter 2 introduces several shin'yō bases that were established in Kōchi Prefecture on the Japanese main island of Shikoku. Each squadron with about 150 to 200 men was assigned to a single base along the coast. Each squadron had either about 50 Model 1 one-man shin'yō boats or about 25 Model 5 two-man shin'yō boats, so the number of shin'yō crewmen totaled about 50 for each squadron. In addition to the 128th Shin'yō Squadron at Tei Base in Yasu Town, this chapter and the rest of the book covers in some detail the following squadrons: 49th Shin'yō Squadron at Nomi Base, 50th Shin'yō Squadron at Usa Base, 127th Shin'yō Squadron at Urato Base, 132nd Shin'yō Squadron at Koe Base, and 134th Shin'yō Squadron at Kashiwajima Base. Tunnels were dug in the rocky hills and cliffs surrounding the bay where each squadron was located in order to hide the shin'yō motorboats from detection and attack. The chapter provides maps of the different shin'yō bases that show the location of the tunnels. There is also a detailed explanation of the organizational structure of the shin'yō bases, since this has importance in trying to understand the source of miscommunications that took place on the day of the explosions at Tei Base. The Kure Naval District's 8th Tokkō (Special Attack) Sentai based at Saeki in Ōita Prefecture included two Totsugeki Units based in Kōchi Prefecture: the 21st with headquarters in Sukumo and the 23rd at Susaki Bay. Tei Base, along with bases at Nomi, Usa, Urato, and Muroto, were part of the 23rd Totsugeki Unit in the northern part of Kōchi Prefecture. The 21st Totsugeki Unit included shin'yō bases in the southern part of the prefecture and also included some bases in Ehime Prefecture. The 128th Shin'yō Squadron at Tei Base had 171 total members including 7 officers, 48 crewmen, 31 maintenance workers, 14 headquarters personnel, and 71 other base workers.

Chapter 3 discusses the situation with the various shin'yō squadrons in Kōchi Prefecture after the Emperor's announcement of surrender on August 15, 1945. Orders came from the 23rd Totsugeki Unit headquarters for the squadrons to be ready to sortie against enemy ships, since there was still a fear that the mainland could be subject to an imminent enemy attack. The five squadrons in the 21st Totsugeki Unit are thought to have been in much the same situation as they were ready to sortie in their shin'yō motorboats whenever an order would come. The young crewmen had been ready to die in shin'yō boat attacks when the Emperor's radio message of surrender was heard. Many of them at various bases after drinking that night made comments among themselves that they still wanted to sortie in order to make suicide attacks. The officers at Koe Base had to order crewmen of the 132nd Shin'yō Squadron in Tosashimizu to halt such plans to sortie as a group and remain on alert to be ready to sortie if orders were given.

Chapters 4 and 5 represent the heart of the book where Hayashi addresses the questions posed on the book cover. Chapter 4 starts with the official account of the accident as published in the Yasu Town History, which states that during the afternoon of August 16 an order by telegraph arrived: "The enemy task force is heading toward Tosa to land on the home islands, so immediately make preparations to sortie." All squadron members took their boats from the tunnels and lined them up along the shore, but when the engines were being adjusted, spilled gasoline suddenly ignited and one of the boats burned up. Orders were given for the men to take cover. There were attempts to put out the fires and to return to the boats after a few minutes when it seemed safer, but the boat fuel tanks overheated and caused huge explosions. This accident destroyed 23 of the squadron's 25 Model 5 two-man shin'yō motorboats, and 111 men died along with many injured. Hayashi then summarizes the results of several personal interviews of the few squadron survivors and other eyewitnesses still living. The eyewitnesses have some discrepancies between their stories, but they talk mostly consistently of multiple explosions, the smell of gasoline in the air, and running to a nearby tunnel to take cover. The author repeats several times in the book that the Navy never conducted an official inquiry as to what happened at Tei Base, which probably was due to the state of confusion that existed within the Navy right after cessation of hostilities. The two survivors who knew the cause of the fire before the explosions had both passed away by the time that Hayashi started his research on the shin'yō boat accident at Tei Base, so it appears that the cause can never be known with certainty.

Shigeo Nagoya, former 128th Shin'yō Squadron member who drove men seriously wounded in Tei Base explosions to the Japanese Red Cross Hospital in Kōchi City.


Chapter 5 presents several different incorrect reports related to the accidental explosions at Tei Base. One was the supposed sighting of the enemy fleet, but the original source of this report is not clear, and naval reconnaissance flights from Kōchi Air Base did not confirm this sighting. Another false report indicated that the masts of 13 enemy warships, which appeared to be cruisers, had been sighted 25 kilometers south of Kōchi City. This message came by urgent telegraph from Kōchi Naval Air Group to the 23rd Totsugeki Unit headquarters in Susaki before 6 p.m. on August 16, 1945. Therefore, when pillars of fire were sighted in the direction of Yasu Town, the 127th Shin'yō Squadron members at Urato Base initially thought in error that the enemy bombardment had begun and that their shin'yō motorboats would sortie soon to attack enemy ships off Shikoku Island. In another incident, the 134th Shin'yō Squadron at Kashiwajima Base along with the 21st Totsugeki Unit in Sukumo did not clearly understand the Emperor's message of surrender, so they remained ready to sortie. Coincidently, an accident similar to the one at Tei Base occurred at Kashiwajima Base at about the same time. Gasoline apparently caught fire at Kashiwajima Base and led to an explosion in one of the tunnels, but this accident destroyed only three shin'yō boats and slightly injured one person in comparison to the Tei Base accident with 111 men killed, many injured, and 23 boats destroyed. This chapter also goes into theories behind the mysterious disappearance of Lieutenant Junior Grade Seisaku Takenaka, commander of the 128th Shin'yō Squadron, during and after the explosions at Tei Base, but a definitive conclusion is never reached, although we know from the book's last chapter that he was not injured and returned home to Ōsaka soon after the incident.

Chapter 6 covers the repatriation of shin'yō squadron members. Parents who heard the news of their sons' deaths had a difficult time in understanding why they were killed in such an accident when the Emperor already had declared an end to the war on the previous day. Each year there is an annual memorial service at Yasu on August 16 to remember the 111 men who lost their lives in the accidental explosions. A monument was erected on the former base site on August 16, 1956, but Hayashi points out that the history engraved on the monument contains several mistakes. For example, the monument states that 111 men of the 9th Shin'yō Squadron lost their lives on August 16, 1945, but actually the correct squadron is the 128th Shin'yō Squadron. Apparently the person who wrote the history for the monument mistakenly picked up "9th" from the 9th group of shin'yō squadrons formed at Kawatana Torpedo Boat Training School. Squadron leader Seisaku Takenaka had the rank of Lieutenant Junior Grade, but the monument history incorrectly states his rank as Lieutenant.

This thoroughly researched book demonstrates how difficult it can be to conclude with any degree of certainty what happened exactly in a specific historical incident, especially when most of the eyewitnesses have passed away.

Related Web Pages

Shin'yō Corps monument to the 111 men
who died for their country at Tei Base
(in former Yasu Town, Kōchi Prefecture)