In the late 1950s, the FV4201 began to take shape: the first tank to be called a main battle tank. The future Chieftain was supposed to combine the characteristics of a heavy and a medium tank. The U.S. and Germany had a similar joint program—the MBT70. It was the latter that drew the attention of Japanese designers who were in close contact with the American side. What interested them most about that project was the hydropneumatic suspension, as their local theaters of operations made it a very desirable addition. Their tank was supposed to combine a low profile with a powerful gun and good armor. However, the Japan Self-Defense Forces command prioritized tanks with an average weight of 35-40 tons. The vehicle turned out to be too expensive, and no prototypes were built.