The 221 Kokutai was organized on January 15, 1944, in Kasanohara, Kagoshima Prefecture (not Kasanbara) near Kanoya. Three days later the new commander of the unit, Lieutenant Commander Himeno Ichiro, a former seaplane pilot, arrived and took command of the unit.
In the beginning, the unit was equipped with no aircraft. The first two Zeros arrived on February 5 from the 2nd Aviation Arsenal in Tateyama, followed by four more two days later. Training started from February 9.
The 221Ku "Sento Shoho" (Combat Report) gives a quite detailed account of the daily activities of the unit and below is a selection of the most interesting entries.
19/2 - Ten zeros arrived from the 1st Aviation Arsenal at Koizumi.
23/2 - Order to organize a unit to take part in the "Togo Operation" (operation east).
[The "Togo Op" was a recurrent plan under which IJNAF units, especially based in Japan mainland, were placed under the command of the Combined Fleet when the need arose.
In this case, following the appearance of a U.S. Fleet near the Marianas, the JN judged that there was a possibility it would continue and raid Japan mainland. As a result, the YokosukaKu was placed under the Combined Fleet and various other units were ordered to be organized to counter the possible threat that never materialized.]
25/2 - Eight Zeros were sent to Kasumigaura to take part in the "Togo Op".
27/2 - Following formation training with nine Zeros, one aircraft, Nakajima c/n 1082, was destroyed during a taxing accident.
28/2 - The unit had: ten operational a/c, seven undergoing maintenance and repairs.
1/3 - One of the Zeros assigned to the "Togo Op" was sent to Koizumi for repairs. The rest were all back to Kasanohara by 8/3.
12/3 - The 1st Aviation Arsenal at Koizumi sent over six Zeros including the one that was sent for repairs.
16-17/3 - Received one A6M2-K trainer from the 21st Aviation Arsenal at Omura and one Zero fighter from Koizumi the next day.
19/3 - Following attack training with six Zeros, one of them was serious damaged during landing. Nakajima c/n 62449.
On the same day, nine Zeros arrived from Koizumi.
25/3 - During shooting practice attacking a target from behind and above, one aircraft, Nakajima c/n 42561, got entangled with the rope of the streamer and crashed in Aryake Bay. The pilot perished.
28/3 - Received one Watanabe K9W1 primary trainer from the 21AA.
30/3 - The unit had: 26 Zeros operational, 12 in repairs, one A6M2-K and one K9W1.
31/3 - After training, one aircraft, Nakajima c/n 72639, suffered serious damage during landing accident.
1/4 - One Zero, "Arashi131", Nakajima c/n 52455, was sent to the 21AA for repairs.
[This entry confirms that the unit used the nickname "嵐" (arashi - storm) and the relative kanji as its tail marking.]
Also, on the same day the entry reveals that the unit had: two A6M Model 52, 26 A6M Model 21, eight in repairs, one A6M2-K & one K9W1. This information clarifies that the Zeros the unit had until the end of March were A6M2 Model 21.
9/4 - One more A6M2-K arrived from the 21AA
29/4 - Received one A6M2 Model 21 from the 265Ku.
1/5 - One Zero, Nakajima c/n81826, was sent to the 22nd Aviation Arsenal for repairs
On the same day, during formation flight training with 12 aircraft, one of them, Nakajima c/n 62446, was seriously damaged during a landing accident.
The unit had: 20 A6M2 Model 21, 19 in repairs, 0 A6M Model 52, two in repairs, two A6M2-K and one K9W1.
6-8-10/5 - Two a/c, Nakajima c/n 8720 & Nakajima c/n 8728, returned from the AA following repairs, while Nakajima c/n 125083 was sent to the AA.
12/5 - During combat training involving four Zeros, Nakajima c/n 62545, stalled and fell in the pine woods near the airfield. The a/c suffered serious damage and the pilot light injuries.
17/5 - Nakajima c/n 62545 was sent to the AA.
20/5 - Order to organize a unit to participate in a "Togo Operation".
On May 19-20, the USN conducted raids against Minami-Tori-Shima (Marcus Island), with aircraft carriers USS Wasp, USS Essex and USS San Jacinto and again a "Togo Op" was enacted in case the U.S. fleet approached the Japan mainland.
21/5 - Nine Zeros relocated to the Katori base for the "Togo Op". They trained until the 24th and returned to Kasanohara on the 25th. The entry, though, mentions that only seven a/c returned.
1/6 - The unit had: 21 Model 21 and 16 in repairs, one Model 52 and one in repairs, one A6M2-K operational and one in repairs and one K9W1.
The same day, received one Model 52 from 11AA.
6-7/6 - Received four Model 52 from the 2nd Aviation Arsenal at Suzuka followed by four more the next day.
12/6 - Trial flights of "Arashi129" and "Arashi137".
On the same day, six Zeros Model 52 were received from the 2AA.
15-16-18/6 - Another order was issued for a "Togo Op". Unfortunately, I don't have details what it was for. The ground crews departed the next day and 24 Zeros relocated to Kisarazu three days later.
19/6 - Following a test flight, Mitsubishi c/n 84897, crashed in a bamboo field during landing. The a/c was seriously damaged but the pilot suffered only light injuries.
23/6 - Seven A6M2 Model 21 returned to the 22AA
24/6 - Mitsubishi c/n 4901 that was participating in the "Togo Op" and was based in Kisarazu, had a landing accident. The a/c was seriously damaged but the pilot was okay.
29/6 - End of "Togo Op". The same day, six Model 52 arrived from Koizumi and ten more from Suzuka.
30/6 - The unit had 14 Model 21 and 11 in repairs, 24 Model 52 and seven in repairs, two A6M2-K and one K9W1.
The same day one Model 52 and two Model 21s were returned to 22AA.
4-6/7 - Another unidentified "Togo Op" order was issued. Two days later, 16 Zeros took off bound for Kisarazu but encountered bad weather and had to return to base.
7/7 - Four A6M Model 52 c65 were sent from Suzuka. One of them, Mitsubishi c/n5018, had to make an emergency landing at SaikiKu and was sent to the 12AA.
[From this entry onward, the Model 52s delivered to the unit are followed by various "c" indications. If you have any idea what these mean, leave a comment.]
9/7 - Four Model 52 c70 and two Model 52 c65 arrived from Suzuka, followed by two Model 52 c57 from Koizumi.
On the same day, during manouver training, Nakajima c/n 2667, fell in the sea of Kagoshima Bay. The a/c sunk, but the pilot was rescued without any injuries.
Again on the same day, during training of two groups of eight aircraft each, involving locating enemy force and engaging in combat, two aircraft, Mitsubishi c/n4894 and Nakajima c/n22283, crashed on each other. Both pilots perished.
10/7 - The unit was reorganized with four hikotai, fighter 308 (CO Lt Hirusawa Hisaya), 312 (CO Lt Shiozuru), 313 (CO Lt Kawai Shiro) based in Kasanohara and 407 (CO Lt Hayashi Yoshishige) based in Kagoshima.
11/7 - The unit received four Model 52 c57 and five Model 52 c58 from Koizumi.
12/7 - During aerial shooting practice, the engine of Nakajima c/n 42560 stopped, the a/c crashed and was seriously damaged but the pilot was okay.
14-15/7 - The unit received one Model 52 c57, one Model 52 c70 and seven Model 52 c59 followed by five more Model 52 c90 the next day, all from Suzuka.
23/7 - One A6M2-K trainer was given to the 308 Hikotai.
25/7 - Seven Model 52 c59 were delivered from Koizumi, seven Model 52 c94 and four Model 52 c95 were delivered from Suzuka. Five Model 21s were assigned to the 308 Hikotai.
31/7 - The unit had: 51 Model 52s and 42 in repair, two Model 21 and 11 in repair, one A6M2-K and one K9W1.
[This entry indicates that the 308 Hikotai is not counted in the unit total.]
2/8 - During training, aircraft "21-46" made an emergency landing in the pine woods on the west side of the airfield. The pilot was okay.
[This is the first entry that mentions the tail marking "21-XX". The unit stopped using the "Arashi"tail marking starting from the July 10 re-organization. Japanese post-war sources mention that the tail marking "21-XX" was assigned to the 313 Hikotai, while the 312 Hikotai used the full "221-XX".]
3-4-10/8 - The unit received four Model 52 c95 and four Model 52 c94, followed by three more Model 52 c52 the next day. All from Suzuka. Six days later, three more Model 52 C81 came in from Koizumi.
11/8 - 16 Zeros Model 52 were sent to Shinchiku (modern-day Hsinchu) in Taiwan.
12/8 - 15 Model 52 c82 were delivered from Koizumi.
15-16/8 - 19 A6M Model 52 were sent to Shinchiku while one was delivered from Koizumi, followed by four Model 52 c82 the next day.
17/8 - 16 Model 52 Zeros were dispatched to Shinchiku.
[The mission of the Zeros sent to Taiwan was air defense as well as sea patrol and ship escort.]
22/8 - Two Model 52 c83 were delivered from Koizumi.
26/8 - During shooting practice performing attacks from the rear and above, two 313 Hikotai Zeros hit each other. The pilot of "21-59" was able to use his parachute and was unharmed while the a/c crashed. The other Zero, "21-60" made an emergency landing at Kanoya. The pilot was okay and the a/c suffered only small damage.
[This entry confirms that the 313 Hikotai Zeros used "21-XX" as their tail marking.]
29-30/8 - Seven Model 52 c32 were delivered from Suzuka and the next day four Model 52 c32 from Koizumi.
31/8 - The unit had: 123 Model 52s and 44 in repairs, four Model 21s and one in repair, one A6M2-K and one K9W1.
By the end of the month, the 308 and 313 Hikotai were based in Kasanohara, the 407 was in Kagoshima and the 312 Hikotai in Shinchiku.
The 313 Hikotai had 20 Model 52 operational and 26 in repair, one Model 21 and five in repair, one A6M2-K and one K9W1.
[This is the last entry for the unit as a whole. The following are entries in the combat reports of each hikotai]
1/9 - The unit had: 20 Model 52 operational and 24 in repair, one Model 21 and eight in repair.
2/9 - During training, two aircraft hit each other. The pilot of "21-A59" managed to use his parachute, but the a/c exploded. The pilot of "21-A53" was okay and the a/c suffered only small damage.
[This is the first entry mentioning the new tail marking of the 308 Hikotai; "21-AXX" The letter "A" was written under the numbers.]
8/9 - Completing training, "21-A10" hit "21-A12" during landing. The first suffered little damage while the latter medium.
29-30/9 - During combat training, one a/c attacking an enemy force of six, "221-D157" was forced to make an emergency landing and stopped upside down. The pilot was okay, but the a/c was damaged.
[This is the first entry mentioning the tail marking "221-DXX". According to post-war Japanese sources, this marking was used by the 407 Hikotai.]
While the 221Ku was training in Kasanohara, a number of photos were taken and these confirm the tail markings the various hikotai used. There are no known photos of aircraft with the "Arashi" tail marking.
Below is a photo from Koku Fan Illustrated #53 featuring a Nakajima-built Model 52 of the 312 Hikotai.
A close-up of another well-known photo from the same publication reveals more 312 Hikotai aircraft. Note that their spinners are either brown or white.
More well photographed are the Model 52s of the 407 Hikotai.
In the detail of a photo found in Model Art #510, we can make out "221-D18" and "221-D60"; both Nakajima built. The tail marking of the one in the extreme left is too blury.
The publication "Tatakau Zero-sen" by Watanabe Yoji, features a photo of the maintenance unit commander of the 407 Hikotai, Lt Amanuma Hikoichi (?). In the close-up, it seems the Model 52 he is standing in front of had a different tail marking before the "221-D14" was applied. It's another Nakajima-built Zero and note the wing hinomaru with the thin white surround.
There are also photos of a number of Model 52s with a "Z" or a "ZII" and under the "221-XX" marking.
Photo detail above from "Tatakau Zero-sen". A Nakajima Model 52 Otsu with dark surrounds on the hinomaru of all top surfaces and two 150litre drop tanks under the wings.
Although no other Japanese publication knows the significance of this "Z" , Watanabe Yoji alone reveals in the above mentioned book, that within the 407 Hikotai there were groups of aircraft assigned to the fighter-bomber role and the "Z" signified this.
Detail of a well-known photo featuring "221-Z27". A Nakajima-built Model 52 Otsu, with two drop tanks under the wings and fuselage hinomaru with a darker surround. Note the white spinner.
Photo detail below from KFI #53.
Another photo of the same aircraft, detail from a well-known photo, showing the two drop tanks and the brown spinner.
If this aircraft line-up is the same as seen in the photo above, then "221-D18" has a white spinner and no wing drop tanks, and the "221-D60" doesn't have drop tanks either and has a brown spinner.