Type 61 The Type 61 ( Japanese : ろくいちしきせんしゃ Kanji : 61式戦車 ) was a main battle tank ( MBT ) developed and used by the Japan Ground Self - Defense Force ( JGSDF ) , built by Mitsubishi Heavy Industries . Development started in 1955 and the vehicle was first deployed in April 1961 . The type number follows the year of deployment . A total of 560 Type 61 ' s were manufactured between 1961 to 1975 , when production ceased . History . After World War II , Supreme Commander of the Allied Powers ( A . K . A . GHQ in Japan ) ceased all military manufacturing and development plants in Japan , making Japan lose the technology to build and manufacture tanks and armoured vehicles ( even though the technology was not well developed . ) However , due to the Korean War , the Supreme Commander of the Allied Powers ordered Japan to re - militarize , forming armed police forces ( National police reserve , later called National security force , then finally Japan ground self - defence force ) and provided M4A3E8 Sherman and M24 Chaffee tanks . However , the average height of a Japanese person at the time was too small for the M4A3E8 , and drivers had difficulty reaching the clutch pedal with their foot . In addition , the M4 was becoming obsolete . The M24 , though it was popular amongst the Japanese crews , was inadequate when facing Soviet T - 34 / 85 s , as seen in Korea . Thus , as the tanks in JGSDF service at the time were obsolete / inadequate , the JGSDF was provided with the option of either purchasing the new American built M46 Patton and , later , the M47 Patton or develop their own MBT in 1954 . Due to the high cost of purchasing American made tanks , and because the M47 did not meet their requirements , the JGSDF decided on developing their own main battle tank , resulting in the development of the Type 61 . Development . The original requirements were : The weight was one of the main concerns since if the first constraint was met , the tank could also be transported by a specially modified truck through most major highways and tunnels in Japan . The second contraint couldn ' t be met due to the mock up development team finding out that the armour would be too thin to protect the vehicle . As a result , the armour weight contraint was raised to 35 tons for a while . However , due to a delays in the production of the planned diesel engine , the tank did not have enough power to attain good mobility . As a result the weight of the armour was reduced . The final constraint was due to light the body build of Japanese people at that time , after examining the M36 Jackson , 90 millimeter ammunition was felt to be the upper limit of what an average Japanese tanker could handle effectively . Additionally due to the mountainous landscape of Japan , it was unlikely that long range engagements would occur frequently and it was thought that a 90 millimeter gun would be sufficient . The first test vehicles , STA - 1 ( completed in December 1956 ) and STA - 2 ( completed in February 1957 ) were built and tested . The results were used to develop the STA - 3 ( completed in January 1960 ) and STA - 4 ( completed in November 1959 ) in 1960 . More improvements were made in 1961 and the deployment of the Type 61 started in the same year . The initial production rate was low , with only ten tanks produced in 1961 and 1962 , increasing to twenty in 1964 and thirty in 1965 and 1966 . A total of 250 had been produced by 1970 , with production continuing at an increased pace until 1975 when it was terminated . A total of 560 were produced . The tanks were phased out of service in the 1990s with 400 in service in 1990 , and 190 in service in 1995 . All were decommissioned by 2000 , 39 years after their original deployment . During this period , the type 61 received minor upgrades in the form of infra red searchlights and / or smoke dischargers . From 1980 , Type 61 ' s began to be supplemented by the more modern Type 74 MBT . Description . The Type 61 is conventionally laid out , with a central turret and the engine located at the rear of the hull . The tank has a crew of four , a commander , driver , gunner and loader . The hull is welded steel , with a cast steel turret . The maximum armour thickness is quoted as 64 millimeters . The driver sits at the front right of the hull , with a hatch immediately above him , and three vision periscopes covering the forward arc . To the drivers left is the transmission , which can be accessed for servicing by removing a large panel on the front of the hull . The commander and gunner sit in the turret on the right side , with the commander provided with a large domed cupola with a hatch on the rear of it . The cuppola has four vision blocks , which are angled upward , and a one meter base stereoscopic rangefinder with x7 magnification . A 12 . 7 mm machine gun was normally mounted on the cuppola for anti - aircraft use . The gunner does not have a hatch and is seated forward of the commander . The gunner has a x6 magnification periscope , as well as a x6 magnification sight . The main gun was the Type 61 90 millimeter calibre rifled gun with a horizontal sliding breach block . The gun is fitted with a t - shaped muzzle brake , which diverts firing gasses sideways , and reduces the amount of dust kicked up by firing . A coaxial 7 . 62 millimeter machine gun is mounted next to the gun . The loader is provided with a small hatch , which has a small flap in it for ejecting spent shell cases by hand . Storage is provided for 18 rounds in the bustle at the rear of the tank , with additional rounds being distributed in various positions inside the tank . A tool storage box was normally mounted externally on the rear of the bustle , and three smoke grenade launchers were mounted on each side of the turret . Two large radio antenna were also attached to the rear of the bustle . The tank was powered by a 570 horsepower Mitsubishi HM21 WT V12 turbocharged diesel mounted at the rear of the hull and exhausting through pipes on either side of the rear of the hull . The engine is coupled to a Mitsubishi manual transmission system . The track is driven from the front , and has six rubber road wheels on each side along with three return rollers . The suspension is a torsion bar system with the first , second and sixth road wheel fitted with hydraulic shock absorbers . The main gun is unstabilized , so firing on the move was impractical , and the vehicle is not fitted with an NBC protection system or deep wading equipment . See also . Type 61 - Type 74 - Type 90 - Type 10