Japan has launched its first new diesel electric submarine, which will complete the plan of the US allies to expand their submarine fleet to 22 after service. The new submarine named "Big Whale" was launched on Wednesday at Mitsubishi Heavy Industries Shipbuilding in Kobe. This is the first ship after Japan's current Soya class ships.

The 'Tai Gui' is a 3000 ton diesel electric attack submarine, measuring 84 meters (275 feet, 7 inches) in length. This design was previously known as the 29SS level, named after the 29 year reign of Emperor Akihito, corresponding to the year 2017 in the Gregorian calendar.

Like the last two ships of the Soyu class, the Taiji will be equipped with lithium-ion batteries as its power source. Since the beginning of the 21st century, Japan has conducted extensive research on the use of lithium-ion batteries on submarines and stated that compared to lead-acid batteries, lithium-ion batteries require less maintenance and can withstand longer endurance at high speeds. Japan is the only known country to have submarines that use lithium-ion batteries. Before joining the Japan Maritime Self Defense Force in 2022, the Taikoo will now undergo renovations and sea trials at the construction site. After being put into use, it will become the 22nd submarine in service for the unit, completing the plan to increase the Japanese fleet to 22.

The upgraded submarine fleet will consist of 9 old Oyashio class submarines, 12 Soryus and Taigei submarines. The Japanese Ministry of Defense has requested the addition of two submarines worth $150 million.

The decision to increase submarine capabilities from 16 submarines was announced in the 2010 National Defense Plan Guidelines, while Japan remained vigilant about China's military modernization and growing confidence in the region.