Indonesian military sources have revealed that the country is planning to expand its submarine fleet from four vessels to 12, in response to China’s repeated incursions into disputed waters in the South China Sea.

Indonesia has the world’s third largest water territory under its exclusive economic zone (EEZ), but currently has just four submarines. By contrast, Japan ranks sixth in water territory and has 20 submarines.

Indonesia originally had five submarines, but lost one—KRI Nanggala-402—during an accident off Bali on April 21. A search and rescue team found that the submarine had sunk to the bottom of the sea and broken into three pieces, killing all 53 crew members. The German-made Nanggala-402 had been in service for 40 years.

Among the remaining four submarines currently in service, two were built in South Korea, and one was produced domestically using South Korean technology.

After the submarine tragedy last month, Indonesian Defense Minister Prabowo Subianto said that the country would increase its investment in military equipment. Indonesia is seeking to reach a joint production agreement with South Korea on submarines, and France, Russia, and Turkey have offered to export submarines to Indonesia.

Indonesian think tank analyst Khairul Fahmi believes if the size of the submarine fleet can be increased to 12, they can conduct intensive surveillance in areas that are difficult to reach by patrol ships and it will reduce the presence of foreign ships around the Natuna Islands.

Indonesia’s expanding of its submarine fleet was in response to the Chinese communist regime’s repeated incursion into the disputed waters. Indonesia considers the waters near its Natuna Islands within its EEZ, while China claims sovereignty over the waters, citing the so-called nine-dash line historical claims within the South China Sea.
The tension between the two counties over the disputed waters has escalated since a fishing boat incident in 2016, when an Indonesian patrol ship intercepted a Chinese fishing boat operating near Natuna. An armed Chinese coast guard vessel entered the EEZ and freed the fishing boat.

In 2020, military and fishing vessels between China and Indonesia had more stand-offs. Meanwhile, Jakarta has complained that Chinese research vessels increased their transit through Indonesian waters, and suspected that they dropped off drones to map the seabed for submarine warfare purposes.

In recent years, the Chinese regime has increased its aggression in the South China Sea with other Southeast Asian countries, including Vietnam in 2019.

Since April, 2021, the tension between China and the Philippines has escalated, as hundreds of Chinese paramilitary vessels posing as fishing boats lingered in the waters near the disputed Whitsun Reef.