Comparing: 121 vs. STB-1

Development began in 1962 on a new medium tank based on the Type 59. The new tank was expected to feature improvements in firepower and armor protection. However, the project was canceled shortly after. Some technical innovations were applied later, in the development of the Type 69 tank. All 121 tank prototypes were destroyed during Chinese nuclear weapon testing.

In the early 1960s, Mitsubishi started development of a new tank that complied with government requirements for armament and defense. The first two prototypes of the STB-1 were manufactured in September 1969 for trials. In 1970 the prototypes were shown to journalists and participated in a military parade.