Quiz #4 - Answer

The answer to this quiz was quite difficult to figure out. There are still various questions we haven't found the complete answer yet but we keep searching and, as always, we will update this post accordingly. 
What was particularly surprising and frustrating, is how little proper research has been done on the "Shiden" units. Scattered information all over the place, one-liners in photo captions and sometimes inaccurate tidbits, cannot be called serious research.
Anyway, let's begin by making clear that the aircraft in the photo is indeed a Kawanishi N1K1-J "Shiden" belonging to the Omura Kokutai.

The school was inaugurated on December 1, 1922. From the beginning of the Pacific War it was assigned patrol and anti-submarine duties in the East China Sea, operating various types of aircraft.

From the second half of 1944, the fighter instructors were assigned to air defense duties and on August 1 (or 10), 1944, the 352Ku was organized in Omura base, see here. On October 25, 1944, Omura was the target of a major raid which set the 21st Navy Aviation Arsenal on fire. "Shiden" fighters from Omura and 352Ku took off to intercept and claimed at least one enemy bomber shot down. During the following days, Omura city was bombed no less than 18 times and both kokutai did their best to provide air defense.

On May 5, 1945, the Omura Ku was disbanded and was placed under the command of the Seikai Kokutai.  

That's the brief history of the unit, mostly from the Japanese Wiki, and the starting point of various complications.

Here's more information we unearthed from the unit's battle reports.

On December 1, 1944, the unit had 52 Zero fighters of which 20 were combat ready, 24 Mitsubishi A6M2-K Zero trainers, two "Shiden" both under maintenance, 14 "Type 2 Trainers" (probably A5M4-K), 18 Type 96 Fighters (A5M "Claude"), five Type 90 Crew Trainers (Mitsubishi K3M "Pine") and five Yokosuka K5Y2 "Akatonbo" trainers. This is the first time any "Shiden" are mentioned in the unit's strength so it's safe to conclude that OmuraKu started receiving the type around that time.

On March 31, the unit had the following aircraft in its strength: 58 Zero fighters of which only nine were operational, 41 A6M2-Ks, 12 Type 2 Trainers, 16 A5M "Claude", five K3M "Pine" trainers, 10 "Akatonbo", and one Carrier Attacker of unknown type. Also, 17 "Shiden" of which seven were hidden to avoid been destroyed by air raids and eight were undergoing maintenance. This leaves only two combat-ready N1K1-Js even though the official document mentions that there were no operational "Shiden" in the unit whatsoever.

The battle reports end on this date.

As mentioned above, the unit was disbanded on May 5. Omura Kokutai documents describe the reassignment of the personnel, and mention that most of the pilots and students were sent over to the 352Ku. Of the 1800  ground crew members, 1630 were reassigned to Seikai Kokutai, 50 to 352Ku, three to 210Ku, 22 to TsukubaKu and 112 to San-in Kokutai.

Unfortunately, there is no mention as to what happened to the unit's aircraft.

Watanabe Yoji in a photo caption on p.184, of his book "Hondo Bokusen" mentions:

"Around March 1945, the following units were equipped with "Shiden": YatabeKu, TsukubaKu, OmuraKu and GenzanKu which were all training units, and 210Ku, 601Ku and Sento 402 Hikotai.

On May 5, five of these "Shiden" units gathered in Tsukuba and were grouped together as Sento 403 Hikotai, together with Sento 402 Hikotai."

This means that, according to Watanabe Yoji, the OmuraKu "Shiden" were reassigned to TsukubaKu and more specifically to the Sento 403 Hikotai.

Akimoto in "Saikyo Sentoki Shiden-Kai", p.147, agrees and mentions that: 

"Around March 1945, YatabeKu begun receiving "Shiden" and this "Shiden-tai" (unit) with 18 aircraft, on May 5, with TsukubaKu, OmuraKu, GenzanKu, 210Ku, were all merged together becoming Sento 403 Hikotai. Also, the Sento 402 Hikotai that was under 601Ku, came under the TsukubaKu as well."

Nevertheless, Model Art #587, mentions on p.149, that the "OS" marking on the "Shiden" signified the "OmuraKu detachment to the SeikaiKu".

The Decal set "Terrible Georges" by "On the Move", 2002, includes a list of all the "Shiden" found at the end of the war and the bases they were discovered at. In Tsukuba there are only 11 "Shiden" but 74 "Shiden" are mentioned at Himeji base. The Himeji factory had no airfield, so the finished aircraft were disassembled and were transported by horse or oxcarts to another assembly factory, where they were put together and then dispatched to various units by the 1001Ku based at Himeji Base. The Sento 402 and 403 Hikotai were located at that airfield in the end of June, so maybe these aircraft belonged to these units. 

The list mentions 77 "Shiden" in Omura, probably including the "Shiden-Kai" of 343Ku.

Below is well-known photo of a Model 52 Hei Zero, having the tail marking "03 798" belonging to the 203Ku. But under that tail marking, we can see that it has an earlier marking; "オ-148", which means it previously belonged to OmuraKu. Of particular interest is the fact that this aircraft was found at the end of the war in Omura base.

One last piece of information. The Seikai Kokutai was one of the few units known unofficially as "Otsu". These kokutai were assigned to certain sectors but did not have any aircraft or crews of their own. They were ground support units with airfield guards, lookouts and transport sections. When the enemy presence was particularly felt in their sector area, various units were assigned to these "Otsu Kokutai" to provide air cover in the area. 

So, to summarize, it is confirmed that Omura Kokutai had more than a dozen of "Shiden" fighters starting from January 1945. The unit was disbanded on May, 1945, and came under the Seikai Kokutai. Most of the pilots were assigned to the 352Ku, while most of the ground crew members were assigned to SeikaiKu and about two dozen to TsukubaKu.

The "mystery" is what happened to the unit's aircraft after it was disbanded. Did the "Shiden" stay in Omura and was there an "Omura detachment" under the SeikaiKu equipped with "Shiden"? Or were they all reassigned to the TsukubaKu coming under the Sento 403 Hikotai? 

Our suggestion based on the above available information is the following; OmuraKu most probably did not have any operational "Shiden" on May 5, 1945. No "Shiden" were sent to TsukubaKu, otherwise Sento 403 would have more than 11 aircraft at the end of the war and wouldn't wait for new ones fresh out of the factories. Note also that no OmuraKu pilots were reassigned to Tsukuba. What OmuraKu sent to Tsukuba was ground crews experienced with the type.

All OmuraKu pilots that could fly "Shiden", were reassigned to the 352Ku and were to fly "Shiden-Kai" fighters of which the unit had plenty. Note that 50 ground crew members were reassigned to the 352Ku, in our opinion those familiar with the "Shiden/Shiden-Kai" types. All remaining aircraft, Zeros and others were reassigned to various units, like the 203Ku, probably coming under the Seikai Kokutai with most of the ground crew members.

In our opinion there was never a "Shiden" equipped "Omura detachment". There was indeed an Omura Detachment but consisted of ground crews.

The "S" in the tail marking did not signify the "Seikai Kokutai" but was used only by the "Shiden" of the OmuraKu; the Zeros had only an "O" on their tail.

Below is the complete photo from which the close up with the "Shiden" tail was taken. In my opinion this is one of the hangars of the 21 Navy Aviation Arsenal in Omura Base with many different types of damaged or destroyed aircraft, from various units, that were to be either fixed or cannibalized for spare parts.

Note in the foreground the L2B3 "Tabby" of the 1081Ku.

If you have more information about the fate of the Omura Kokutai "Shiden" please feel free to leave a comment or email us.