Submarine -Desperate War of Japan in the Pacific-

Submarine

Plan to visit Europe by submarine

Yoshida Shigeru^[15] was arrasted by Kempei because he had a copy of Konoe's address to Mikado for peace on 15 April 1945^[17]. Yoshida visited vice admiral Ozawa^[16] and asked whether a submarine of IJN could ferry him to Europe in June 1945 in order to negotiate a peace treaty. Yoshida was told to go by Akizuki. Akizuki was a son of Lord Akizuki. Ozawa was a son of samurai of Akizuki Han. His wife was a daughter of Akizuki clan.

Why did Yoshida think of Siberia Railways? Russia approved of Japanese diplomat's commnunicating to Europe.

Rescue crews

USN used submarines were used to rescue air crews. A damaged B-29 flew to the surface where a submarine waited for bailing out crews off 1 mile coast. The submarine merged on the surface in 10min^[2]. How did submerged rescue submarines receive wireless signals? For example, USS Archerfish had patrolled and waited for rescuing B-29 crews near Mikura Island on 28 November 1944. Without rescue job, Archerfish began tracking and sank aircraft carrier Shinano by radar on 28 November 1944.

Former President George Herbert Walker Bush's TBF was shot down near Chichi Jima. He was picked by USS Finback. He was a student and volunteered for USN, when the Pacific War broke. While IJN Ro-105 rescued a Japanese air crew on 6 November 1943 near Bougainville of Solomons^[1]. I think this was few cases.

Threat to battleships

IJN battleship Yamato and Musashi were afraid of US submarines. They could not run alone. Two or three destroyers always had to escort them, when they ran. Actually battle cruiser Kongo sank off Taiwan by a submarine for the first time in naval history on 21 November 1944. They had better stay still like Hitler ordered Kriegsmarine. Were German battleships afraid of RN submarines? German battleships actioned and ran without escort of destroyers.

Submarines built in 1945

Built submarines in 1945
No.	Date	Displacement	Shipyard
I-401	Jan08	3,440t	Sasebo
I-402	Jul24	3,440t	Sasebo
I-201	Feb02	1,070t	Kure
I-202	Feb12	1,070t	Kure
I-203	May29	1,070t	Kure
I-373	Apr14	1,660t	Yokosuka
Ha-103	Feb03	370t	Kawasaki
Ha-105	Feb15	370t	Kawasaki
Ha-108	May06	370t	Kawasaki
Ha-107	Feb07	370t	Kobe
Ha-109	Mar10	370t	Kobe
Total		13,600t

Japan built such submarines at desperate effort in 1945. I-200 class ran at submerged 19kt. Ha-101 class was submerged transports which supplied in the central Pacific. I-373 was submerged transport with no torpedo tubes. But the submarine might equipped snorkel for the first time in WWII of IJN.
I-200 class
Ha-101 class
I-373
Nihon sensuikan shi

USN took I-400, I-401, I-14, I-201 and I-202 to Hawaii in January 1946^[3]. I think USN was interested because I-400, I-401 and I-14 carried 2 or 3 sea plane bombers. I-201 and I-202 ran faster submerged than surface.

Midget sumarines powered of IJN and Kriegsmarine
Type or Name Type tei Seehund

Lenght [m] 28 12.0

Width [m] 2.0 1.7

Displacement [t] 50(submerged) 14.9

Horse power
(Surface/Submerged) - 60/12

Speed
(Surface/Submerged)[kt] 12/16 7.7/6.0

Range
(Surface/Submerged) 600nm @ 8kt/
125nm @ 2.5kt 480km @ 7kt/
38km @ 3kt

Torpedo 45cm x 2 53.3cm x 2

Crews 5 2

Built date 1945 Mar- 1944

Production 100 67

Shipyard Kure, Tamano Kier, Danzig, Ulm

IJN made midget subamrines called Ko-hyoteki to intercept US fleet originally, but it was used to invade and attack in harbors actually. Its endurance was only 80 min at 6kt. So Type hei was developed to charge batteries, which had a gas engine. This type were posittioned islands near Japan mainland. Type tei also was developed to intercept freighters of convoy landing US arimes. Only 20 type tei could do operaion because of shortage of trainned crews. A cite shows photos of Type tei^[5].
Taga p.195
Hashimoto p.255
Hirota p.366

Torpedo

USN submarine torpedos do not adjust depth to run in the Pacific War. Why could USN torpedos control depth? IJN torpedos ran at the precision of 0.5 m depth. They fluctuated 10 or 15 times in the range of the precision while running 1,000 m^[4]. 1 atm is equivalent of 1 kgf/cm² and 10 m height of water. So pressure of 0.5 m is 0.05 kgf/cm². How didn't mechanical servo of USN torpedoes work well? Wikipedia explains that USN did a test using a light dummy head. Most submarine skippers simply set their torpedoes running depth to zero, risking a broach. By August 1942, the faulty running depth situation was in hand and submarines were getting more hits with the Mark 14^[6].

TDC and Zigzag

Japanese ships sailed zigzag to avoid torpedos of submarines in the Pacific war, when they was able to use such the way. But US fleet submarines had a TDC to track a target and gyroing. The TDC computed automatically. Otherwise IJN submarines used a primitive drawing table or board. Uboats used a simple mechanical computer compared to USN.
Hirota p.249, Hashimoto p.372, Enright p.242-260

I-58 had to run zigzag near Yaku Island on the way to Okinawa Battle in the south of Kyushu on Apr 3rd 1945. Hashimoto p.292

Submarines in the Pacific nowdays

JMSDF, PLAN, South/North Korean, Russian and US submarines are in service in the north of the Pacific now, while US, IJN, Russian, RN, Dutch and Kriegsmarine submarines were in actionin the Pacific War. Japan worried oil ferry because of USN submarines in the Pacific War. The US subs were in duty far from Pearl Harbor or Free Mantle at first. PLAN or Korean subs can threaten Japanese oil reservers in Kagoshima from their ports easily.

[1] Hashimoto, p146
[2] Superfortress B-29, p223
[3] Shusenji no teikoku kantei, p224
[4] 雷道上 no 問題
[5] Tokusyu senkoutei senshi(Ko-hyoteki)
[6] Mark 14 torpedo
[7] 中国潜水艦、国旗掲げ浮上航行　鹿児島県沖、海自が確認
[15] Yoshida Shigeru
[16] Ozawa Jisaburou
[17] NHK6, p98-99