I noticed that MBT doesn't have the lengthy design notes for each nation that WW2 does; so I started to do a first stab at it; to provide some background for Japan.
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Sources:
BOOKS/Thesises/Articles
Crisis Support of the Korean War in
Army Logistician by Kenneth W. Carroll
A History of Japan’s National Police Reserve 1950-1952: Army or Constabulary? by Thomas W. French (PhD thesis, 2010)
Maneuver and firepower : the evolution of divisions and separate brigades by John B. Wilson
Fear of World War III: Social Politics of Japan's Rearmament and Peace Movements, 1950-3 by Masuda Hajimu in the
Journal of Contemporary History, Vol. 47, No. 3 (JULY 2012), pp. 551-571
CIA Sources
https://www.cia.gov/library/readingr...00580001-3.pdf
WEBSITES
http://russianships.info/eng/warship...amphibious.htm
https://www.tanknet.org/index.php?/t...apanese-tanks/ - TANK NET THREAD
https://ja.wikipedia.org/wiki/%E9%99...A1%9B%E9%9A%8A
https://ja.wikipedia.org/wiki/%E8%AD...82%99%E9%9A%8A
https://ja.wikipedia.org/wiki/%E7%AC...82%AB%E8%BB%8D)
https://web.archive.org/web/20160606...5_Kuzuhara.pdf
https://ja.wikisource.org/wiki/%E8%A...A6%8F%E7%A8%8B
https://ja.wikipedia.org/wiki/M24%E8...88%A6%E8%BB%8A
https://ja.wikipedia.org/wiki/M41%E8...88%A6%E8%BB%8A
https://ja.wikipedia.org/wiki/M15%E5...B5%B0%E7%A0%B2
https://ja.wikipedia.org/wiki/M16%E5...B5%B0%E7%A0%B2
https://ja.wikipedia.org/wiki/%E7%AC...BB%8A%E7%BE%A4
https://www.mod.go.jp/gsdf/nae/7d/he...ku/enkaku.html
https://ja.wikipedia.org/wiki/%E7%AC...BB%8A%E7%BE%A4
http://combat1.sakura.ne.jp/61SHIKI.htm
https://forum.warthunder.com/index.p...r-army/page/2/
https://ru.wikipedia.org/wiki/%D0%94...B4%D0%BE%D0%B2
THE U.S. ERA (1945-1950)
From 1945 to 1950, the defense and security of Japan was entirely the responsibility of the United States; which provided it through two Field Armies:
Sixth Army (September 1945 - 26 January 1946)
Eighth Army (September 1945 - July 1950)
Originally, the demarcation of control was along the line ITOUGAWA to ODAWARA, with Sixth Army taking control over Western Japan, while Eighth Army controlled Eastern Japan. However, due to Sixth Army being established much earlier and fighting longer, its units had many "high-points" men and the decision was made to withdraw it for demobilization, and give Eighth Army full control over Japan.
During this period, a significant policy change took place that would have effects for U.S. Forces in Korea. Because the M4 Sherman and M26 Pershing were too heavy for most bridges in Japan, Eighth Army placed them into storage, and instead relied on the M24 Chafee for in-theater tanks per U.S. Far East Command orders, as USFEC wished to avoid excessive damage to Japanese infrastructure.
The National Police Reserve (警察予備隊, Keisatsu Yobitai) Era (1950-1952)
Following the outbreak of the Korean War and the movement of most of Eighth Army to South Korea (where it has remained since then), pressure mounted to organize a Japanese (para)military force to provide for the security of Japan.
On 8 July 1950, General MacArthur presented a letter to PM Yoshida requesting the establishment of a "police force" to handle internal security in Japan. This was followed by a speech before the Diet by Prime Minister Yoshida on 7 August 1950, where he stated:
“The Korean War is not a fire across the river. Communist elements in this country are conspicuously baring their characteristics of fifth columnists as well as their traitorous plots. Accordingly, we are determined to take vigorous steps to prevent red disturbances.”
Three days later, on 10 August 1950 the National Police Reserve (警察予備隊, Keisatsu Yobitai) was accordingly established. On 17 August 1950, Japanese men all over the country took the entrance exam for the NPR at 180 places across Japan. By the end of the day, some 203,843 had applied for the 75,000 openings in the NPR (the ultimate total was 382,003 applicants).
By 28 September 1950, the first NPR cadre forces were ready, having undergone a four-week training period.
Initially, the NPR was rather lightly armed, having 480 vehicles and 75,000 carbines; being more of a paramilitary rear-area security force than an actual combat formation, as per MacArthur's wishes. The choice of the M1 Carbine as the primary infantry weapon for the NPR was another conscious decision as well; being seen as politically safer than using still-exant supplies of Imperial Japanese Army munitions left over in Japan.
During this time period, Colonel Kowalski of SCAP was informed in August 1950 that the final US division would leave Hokkaido in September 1950 for Korea, leaving the island bare of any defenses to a Soviet invasion. Accordingly, he was ordered to rush the training of 10,000 NPR troops and transport them to Hokkaido as quickly as possible.
Because of time pressure, there was no time to train the recruits at the induction centers; and these recruits were instructed in how to care for and use their M1 Carbines while on the trains transporting them to Hokkaido, and they arrived at their new camps in Hokkaido just as the US troops were departing for Korea.
A year later, the XVI (US) Corps, consisting of the 40th and 45th Infantry Divisions (both National Guard) arrived in Japan in April 1951, and were charged with the defense of Hokkaido and Aomori on 10 May 1951, plugging this perceived "hole" in Japanese security from Soviet invasion.
On 29 December 1950, the first basic organization of the NPR was published, consisting of four division equivalents of 13,000 men each, with the units being assigned as:
第1管区隊 (Kanto Plains and Central Honshu)
第2管区隊 (Hokkaido and Northern Honshu)
第3管区隊 (Southern Honshu)
第4管区隊 (Kyushu and portions of Southern Honshu)
However, Chinese intervention in the Korean War changed everything. Following the fall of Seoul on 3 January 1951, MacArthur reversed course and declared:
“in light of current conditions, the delivery of equipment and supplies to the National Police Reserve is a matter of critical urgency, as high a priority as any request related to the Korean War, and any delay in this is unacceptable.”
Accordingly, he then submitted to the Defense Department a “List of Weapons Required by the National Police Reserve of Japan":
36 x M24 Light Tanks
307 x M26 Medium Tanks
25 x M4A3(76) Medium Tanks
31 x M45 (105) Medium Tanks
41 x M32 Tank Recovery Vehicles
50 x Bulldozer Equipped Tanks
135 x M16 MGMG Quad .50 Half tracks
135 x M19 Duster 40mm SPAA Guns
2,198 x M20 Super-Bazookas (3.5")
228 x M2A1 105mm Howitzers
76 x M1 155mm Howitzers
155 x 4.2" Chemical Mortars
816 x Recoilless Rifles
2,480 x Machine Guns
A careful reading of existing US Army TO&Es of the period reveals that this basic package of equipment is equivalent to four US Infantry Divisions.
A few days later on 7 January 1951, the Defense Department replied to MacArthur's list by suggesting that the NPR be structured as light divisions, rather than heavy divisions.
MacArthur countered by pointing out that South Korean light divisions hadn't withstood the North Korean People's Army's tank assault, and that a National Police Reserve without heavy weapons wouldn't be able to respond to
“any and all contingencies including an all-out invasion of Japan by foreign armies equipped and trained in line with the Communist doctrine.”
Unfortunately, delays in the approval of heavy weaponry for the NPR lasted through 1951 and into 1952, especially after MacArthur was fired in April 1951 and no longer could advocate for Japanese re-armament with his personal charisma and five-star rank.
For example, on 27 October 1951 the US Army planned to enlarge the NPR to:
8 Infantry Divisions by December 1952 (121,600 men in frontline combat units and 34,400 men in HQ & Service units)
10 infantry divisions, 37 artillery battalions, 40 anti-aircraft battalions, 3 combat engineer groups, 3 chemical mortar batteries, three armoured cavalry regiments and three medium tank battalions by December 1953 (300,000 men in total)
This was aborted by clashes with the State Department who believed that transforming the NPR into a military before the formal conclusion of a peace treaty with Japan could undermine support for such a treaty among wartime allies such as Australia and New Zealand.
General Matthew Ridgway, Commander-in-Chief, Far East (CINCFE) and one of the stronger "hawks" for Japanese re-armament agreed, and so, the introduction of heavy weaponry (defined by the State Department as: Tanks, Artillery, Recoilless Rifles, Mortars larger than 81mm, and rocket launchers larger than 3.5 inches) had to wait.
The training phases of the NPR were:
Phase I Training (August 1950 - January 1951) (Individual Training)
M1 Carbines
480~ unarmored vehicles such as the Jeep were provided
Phase II Training (January 1951 - May 1951) (Company Training)
M1919 Browning MG
60mm M2 Mortar (large issues began arriving around 20 June 1951)
75mm M20 RCL
M15A1 SPAA Gun (16 provided)
M16 MGMG SPAA Gun (48 provided)
Phase III Training (June 1951 - October 1951) (Battalion Training)
M1 Garand Rifles
M1911 Pistols
M1918 Browning Automatic Rifles (BAR)
81mm M1 Mortar (450 provided in September 1951)
2,130 miscellaneous vehicles provided in July 1951
Phase IV Training (October 1951 - January 1952) (Job Specific Training)
Phase V Training (February 1952 - June 1952) (Battalion + Special Skills Training)
M20 Super-Bazookas (3.5") (443 provided)
During Phase V training in March 1952, approval was given to establish the Soumagahara Special Training Unit to train NPR troops to handle heavy weaponry. Additionally, in a 24 March 1952 directive to all US military advisors attached to the NPR, they were notified that they would no longer have any direct command authority over Japanese forces as of 3 May 1952.
At Soumagahara, training of the NPR with tanks and howitzers began 7 April 1952 on a U.S. military base 21 days before the Treaty of San Francisco came into force; during a time that the US and Japan were still technically at war.
Phase VI Training (June 1952 - September 1952)
During this phase, the U.S. JCS finally approved the release of heavy munitions to the NPR in July 1952, with releases beginning in August.
M24 Chaffees (40 provided in August 1952)
105mm M2 Howitzers (154 provided in August 1952)
15,000~ miscellaneous vehicles provided in August 1952
The National Safety Force (保安隊, Hoantai) Era (1952-1954)
Following the enactment of the National Safety Agency Law, the National Safety Agency was established on 1 August 1952, and the National Police Reserve was subordinated to it.
This state of affairs lasted just two and a half months, until the National Police Reserve was amalgated with the Maritime Safety Agency on 15 October 1952 to become the National Safety Force (保安隊). Also created at the same time was a unified command structure, which would go on to become the JCS of the JGSDF.
Also during October 1952, additional heavy artillery arrived in the form of the 155mm M1 Howitzer, leading to the National Safety Force's end of October strength of:
190 x Tanks
72 x 155mm Howitzers
156 x 105mm Howitzers
Expansion of the NSF to 110,000 men was also authorized.
On 22 November 1952, the first operational tank unit of the NSF, the Independent 1st Special Vehicle Battalion (1特車大隊) was formed at Camp Shinmachi in Gunma Prefecture on the Northern Kanto plain with M24 Light Tanks.
The reason for the unusual naming of the tank units was political. Because of Article 9 of the Japanese Constitution, rather than calling armored vehicles tanks (戦車), they were instead called Special Vehicles (戦車, Tokusha).
Little more than a year later, on 8 July 1953, the 1st Special Vehicle Battalion moved to Camp Minami-Eniwa on Hokkaido, beginning the long standing Japanese practice of assigning the newest (or heaviest) vehicles in the force to Hokkaido to guard against any potential Soviet/Russian invasion.
The Japanese Ground Self Defense Force (陸上自衛隊; Rikujō Jieitai) Era (1954-Present)
On 1 July 1954, the National Safety Agency was reorganized into the Defense Agency (防衛庁), and the following changes took place:
The National Security Forces became the Japanese Ground Self Defense Forces (JGSDF)
The Security Forces (former Coastal Safety Force & Minesweeping Force) became the Japanese Maritime Self-Defense Forces (JMSDF)
The Japanese Air Self-Defense Forces (JASDF) were created.
1954: The M4A3E8 Sherman
During 1954, the JGSDF received what could be called their first "main battle tank", the M4A3E8 Sherman. Despite being considerably more powerful in both armor and firepower than the M24 Chafee, the Sherman was not as well liked by the JGSDF, due to several factors.
1.) The Sherman had been built around the average American male, presenting considerable ergonomic problems for the average Japanese driver who had difficulty in reaching the clutch pedals in certain positions, such as when standing up.
2.) The Chaffee was small enough to fit the average Japanese and had an automatic transmission, vastly simplifying driving.
3.) The Sherman was much heavier (33,700 kg versus 18,400 kg) than the Chaffee, making transportation of the Sherman throughout Japan a problem; something that has persisted to this day with JGSDF armor.
Despite all these issues, the Shermans were preferentially deployed to Hokkaido, in keeping with traditions of the heaviest and most capable equipment going there.
1955: Development of the Type 61 (61式戦車, Roku-ichi Shiki sensha) MBT
Around 1954, the United States made it known to Japan that the M46 Patton and M41 Bulldog tanks in service with US forces in the region would be modernized/rebuilt in Japan, and as such, they would become easily available for future MDAP aid, along with the more advanced M47 Patton.
In 1955, the development of a all-new main battle tank in Japan was begun, due to several factors:
A.) The ideal maximum width (at the time) of JGSDF tanks had to be 3 meters or less, due to the Japanese rail loading gauge. The M46 Patton was 3.51m wide, disqualifying it from serious consideration.
B.) Due to the ergonomic problems encountered with the Sherman, future tanks should be designed around Japanese stature, rather than accepting foreign equipment which may not fit.
C.) A desire to build an internal domestic defense industry, rather than relying on others for Japanese defense.
Early development goals in January 1955 for the Medium Special Vehicle (中特車) (ST) centered around a 25 tonne vehicle with a 90mm gun, a little bit in-between the M24's 18.4t combat weight and the Sherman's 33.7t combat weight.
By May 1955, the goals were a 30 tonne tank with 90mm gun with 2.8m width (or lesser). This was to change with the acquistion of two M36 90mm Tank Destroyers for research purposes in June 1955. Tests with the M36's revealed that a vehicle of 30~ tonnes mass was necessary for stable shooting of a 90mm caliber gun; and thus by December 1955, the ST had become a 35 tonne vehicle.
Testing of various ST prototypes (STA-1 through STA-4) continued through 1956-1960, until a final design had been settled upon, and in December 1960, it was decided to adopt the final ST design as the JGSDF's new MBT.
Accordingly, in April 1961, the ST was designated the Type 61. Due to problems in setting up production, the first production Type 61 MBT wasn't delivered until October 1962. Production continued from 1962 to 1974, with 560 vehicles delivered.
According to Japanese television, the Type 61 had it's formal retirement ceremony on 31 March 2001, though most tanks had been retired by the year 2000.
1954-1958 The First Post-War Japanese Paratroopers
In September 1954, the first Japanese students started training with the US 187th Airborne Regiment, and on 8 October 1954, the first post-war Japanese paratroopers went out the door from a C-46 Commando of the JASDF.
This was followed by the formal establishment of the 1st Airborne Brigade on 25 June 1958.
1960: The M41 Walker Bulldog Light Tank
Despite the introduction of the Type 61, there was still a desire for a lighter tank to complement the ST/Type 61, as it was felt that a 35 tonne vehicle would be too heavy for operation in the mountainous regions and rice paddies of Japan. Thus in 1960, it was announced that the M41 Walker Bulldog (at 23.2t) would replace the M24 as the JGSDF's front line light tank.
1962: Dropping Pretenses
On 18 January 1962, the JGSDF finally dropped most pretenses in their unit designations, with:
1st Special Vehicle Group (第1特車群) becoming the 1st Tank Group (第1戦車群)
101st Special Vehicle Battalion (第101特車大隊) becoming the 101st Tank Battalion (第101戦車大隊).
1964: Development of the Type 74 (74式戦車, nana-yon-shiki-sensha) MBT
With the pending introduction of more modern MBTs across the world such as the:
M60 Patton (USA)
Leopard I (W.Germany)
AMX-30 (France)
Japan began to look closely at improving their tank fleet. Apparently a single prototype Type 61 was modified with a larger caliber main gun [Type 61 (Revised) / 61式戦車(改) ], but in the end, the decision was made to go with an all new tank. Development of the various components took several years:
10ZF Air-Cooled Diesel (1965-1967)
MT-75 Semi-Automatic Transmission (1964-1967)
The first prototype (STT) initally used the engine and tracks of the Type 61 to test the hydro-pneumatic suspension; but in 1967, the 10ZF diesel and MT-75 transmission were installed for testing, along with a prototype 105mm turret. By 1969, two more prototypes (STB-1 and STB-2) had been completed, followed by STB-6 in 1970.
Interestingly enough, the STB-1 prototype had a passive infrared night vision system, but it was eliminated for the STB-2 prototype in favor of a cheaper active infrared system. The design was finalized in 1974 and production was undertaken by Mitsubishi Heavy Industries from 1975-1989, with 873 vehicles being built. Currently (March 2020) there are 136 Type 74 still in service.