JGSDF's main tank M4 became obsolete in the
late of 1950's, and difficulty began in that maintenance. The
U.S.A. in those days finished manufacturing of M4 already, and
was manufacturing M47 and M48.
JGSDF of those days had 2 choice ways. One way
importing M47 or M48 from the U.S.A, and another way is complete
They determined plainly, It's complete domestic
As that reason...JGSDF made much of the transportation by train
about tank unit in those days. Therefore their tank's width must
be less than 3m. If tank exceeds this width, they have the possibility
that an accident occurs in the passage of tunnel and an trains
intersection. And that weight is limited in 35t by loading ability
of freight train. Because M47's width is 3.52m, it didn't satisfy
In this way, the domestic tank development in
Japan restarted after a blank of 10 years from 1945.
The main gun is 90mm caliber 52, It was west
world standard in those days. "Nihon Seikou" contracted
the development of this gun. They began the gun development of
high muzzle velocity and light weight to surpass U.S.A's 90mm
gun. "Mitsubishi" contracted the power unit, the hull,
other general development.
Some prototype was built before a mass production.
I comment on those prototype at the following.