This tragedy is arguably the Indonesian Navy’s worst peacetime loss, and raises important questions for Indonesia’s defence policymakers. A thorough and independent investigation to identify its primary cause is urgently needed, as a form of accountability to the perished crew and to prevent a similar tragedy from happening in the future.

The Nanggala had previous issues with faulty systems or instruments. In 2012, three crew members were killed in a failed torpedo drill due to a faulty torpedo hatch. The onboard multifrequency underwater telephone communication system was defective throughout the Nanggala’s final and fatal exercise, compromising communication with other assets. Officers who previously served onboard the Nanggala further attested that they had experienced a power blackout, during which the submarine’s controls were inoperative. Her final captain, the late Colonel Heri Oktavian, had also privately voiced concern regarding the submarine’s readiness due to maintenance and repair delays.

The Navy, like all branches of Indonesia’s military, needs to review its safety protocols and adopt a more stringent culture of safety. It should review its approach to the safety of its personnel and equipment during training operations, even if that means reducing the number of training hours per operational unit. More importantly, the entire military needs to conduct a thorough audit to assess the readiness of its defence equipment.

The Indonesian Navy hastily organised a search party by deploying 21 vessels of various types to locate the missing Nanggala. It was the Navy’s own hydrographic survey ship, the Rigel-933, that identified the submarine’s presumed location and immediately sent a distress signal to the International Submarine Escape and Rescue Liaison Office (ISMERLO) calling for international assistance.

At the same time, the Nanggala incident exposes the Indonesian Navy’s limited capability to conduct underwater search and rescue operations. Under its green-water navy roadmap, Indonesia aspires to strengthen its existing submarine fleet to 10–12 vessels and has signed a contract to procure three submarines from South Korea.

But before the incident, developing supporting capabilities for submarine operations, such as submarine rescue, had not been a top priority. The Navy tabled a procurement program for a submarine rescue vessel in 2019, which will hopefully now be revisited as a priority. The accident makes it increasingly clear that Indonesia’s aspiration to expand its submarine fleet needs to be accompanied by a commensurate investment in supporting capabilities, including underwater search and rescue capabilities.

The salvage process started in early May 2021 with the assistance of three Chinese salvage vessels. Given the recent discovery of alleged Chinese maritime reconnaissance activities in Indonesia’s waters, this invites the question of whether this Chinese help was an effort to sway Indonesia’s position in the broader context of the militarisation of the South China Sea. These events show that Indonesia relies heavily on external parties for submarine rescue capabilities. Given this, managing existing ties with ISMERLO member countries as well as other submarine-operating countries is critical.

But as one maritime security expert highlighted, even international cooperation has its limits given that any partnering country has to relocate their rescue assets to where they are needed. Ultimately, Indonesia needs to develop its own submarine rescue capability. Cooperation with international partners should play a part in this process. The Indonesian Navy should undertake a knowledge exchange program and joint submarine rescue exercises with international partners to develop expertise and technical knowledge in submarine rescue operations.

These initiatives will close the Indonesia’s knowledge gap with international counterparts and improve its practices in operating and maintaining submarine systems. Consequently, such programs should not only involve submarine crews, but also units responsible for maintaining vessels.

These are some hard lessons that the Indonesian Navy, and perhaps the Indonesian government, should take from the Nanggala incident. It is a sobering reminder that the Indonesian Navy is far behind its green-water navy aspirations. But hopefully, the costly sacrifice of the submarine’s crew will instigate a new approach towards operational safety and improve the Indonesian Navy’s capabilities.

Sigit Suryo Nugroho is a graduate of the S Rajaratnam School of International Studies (RSIS), Nanyang Technological University, Singapore.

Keoni Marzuki is an Associate Research Fellow with the Indonesia Programme at RSIS, Nanyang Technological University, Singapore.