[1] This type of torpedo, like many other modern Japanese weapons systems, is not exported.

At the end of the Cold War, Soviet attack submarines were capable of moving at higher speed and diving at lower depth, rendering the torpedoes used by US navy and the JMSDF, like the Mk-46 torpedo, less able to deal with them.

The US launched a new type of torpedo, the Mk-50 using an infrared detector and a closed-loop pump with an integrated processing unit for analyzing underwater sound waves for target acquisition.

Soviet submarines, however, have developed adaptive capabilities, such as the use of trap baits and interference of the detection system, making it harder for the torpedo to find its target.

In 1989 a new torpedo project by Japan, G-RX4, was launched to develop the necessary upgrades and start making prototypes.