Indonesia Accelerates Naval Modernization: Major Upgrade Launched for Two Bung Tomo-Class Frigates

(DEFENCE SECURITY ASIA) — Indonesia is advancing a major milestone in its maritime modernization program by launching the upgrade of two additional Bung Tomo-class frigates, KRI Bung Tomo (357) and KRI John Lie (358), marking a decisive effort to reinforce the country’s maritime defence posture across its strategic 5.8 million square kilometres of ocean territory.

This new modernization phase, announced on November 22, 2025, forms part of the Indonesian Navy’s (TNI-AL) long-term fleet enhancement roadmap designed to secure an archipelago of more than 17,000 islands that sits astride some of the world’s most important sea lines of communication.

Indonesia’s maritime security ecosystem remains challenged by illegal fishing syndicates, transnational smuggling networks, territorial friction in the Natuna Sea, and the strategic risks posed by increasingly assertive regional actors operating close to Indonesian waters.

The Bung Tomo-class frigates—acquired from Brunei in 2013—have long served as core assets in TNI-AL’s surface combatant inventory and continue to underpin the service’s aspiration to maintain a credible, multi-role fleet capable of enduring high-tempo maritime operations.

With the third ship, KRI Usman Harun (359), already undergoing mid-life upgrades since 2020, the decision to modernize the remaining two frigates ensures that all three vessels will remain operationally viable well into the 2030s, bolstering Indonesia’s maritime deterrence posture.

The modernization program is led by Dutch naval engineering firm Nevesbu in collaboration with Thales Netherlands and Indonesia’s PT Len Industri, forming a trilateral industrial partnership that supports Indonesia’s Minimum Essential Force (MEF) doctrine—an overarching defence transformation framework targeting full naval capability by 2029.

This ongoing frigate enhancement effort will integrate new generation sensors, weapon systems, and a modernized combat management suite, transforming the Bung Tomo-class into versatile multi-mission workhorses capable of executing anti-surface warfare, maritime interdiction, constabulary operations, and humanitarian assistance missions in increasingly contested waters.

FROM BRUNEIAN ORIGINS TO INDONESIAN SERVICE: THE COMPLEX JOURNEY OF THE BUNG TOMO-CLASS

The Bung Tomo-class traces its origins to a 1995 contract between the Royal Brunei Navy and BAE Systems Marine—then operating as Yarrow Shipbuilders—amounting to approximately £600 million (about USD 740 million / MYR 3.47 billion) for three multi-role light frigates (MRLFs) based on the F2000 design.

Originally designated as the Nakhoda Ragam-class, these ships were built with a high degree of automation suited for Brunei’s modest naval footprint, enabling operations with as few as 79 crew members while maintaining advanced surface and sub-surface capabilities.

Construction began in the late 1990s at BAE’s Barrow shipyard, culminating in the launch of KDB Nakhoda Ragam (now KRI John Lie) and KDB Bendahara Sakam (now KRI Usman Harun) in 2001, followed by KDB Jerambak (now KRI Bung Tomo) in 2002.

However, the program became mired in contract disputes involving cost overruns and disagreements over performance requirements—particularly the ships’ ability to operate effectively in tropical environments—leading Brunei to reject the vessels outright in 2004.

As a result, all three ships remained mothballed for nearly a decade, creating a unique opportunity for Indonesia to acquire the vessels at a deeply discounted rate.

Jakarta purchased the entire class in November 2012 for roughly one-fifth of the original contract value—approximately £120 million (USD 148 million / MYR 695 million)—plus refurbishment costs, representing one of the most cost-effective naval acquisitions in Southeast Asian history.

The purchase aligned with Indonesia’s post-tsunami naval reconstruction phase following the 2004 Indian Ocean catastrophe, which exposed severe gaps in the country’s maritime response capability and prompted a long-term modernization agenda.

The ships were commissioned between July and December 2014, and were reclassified from corvettes to frigates to reflect their enhanced operational roles and the expanding mission profile envisioned by TNI-AL.

All three vessels carry historically resonant names, with KRI Bung Tomo honouring Sutomo, a pivotal figure in the 1945 Battle of Surabaya; KRI John Lie named after a key Indonesian independence-era naval commander; and KRI Usman Harun commemorating a controversial serviceman involved in the 1963 Macassar Strait incident.

Early operational deployments demonstrated the class’s versatility in non-combat roles, including KRI Bung Tomo’s participation in the recovery mission for AirAsia Flight 8501 in 2014, where it executed debris retrieval and diver support in hostile sea conditions.

KRI Usman Harun further showcased the class’s utility by locating the aircraft’s flight recorders using its Thales TMS 4130C1 sonar, reinforcing the ship’s reputation as a capable platform for both peacetime and crisis-response missions across Indonesia’s maritime domain.

By the early 2020s, however, the ships’ legacy systems—including the increasingly outdated MBDA Seawolf surface-to-air missile, retired globally in 2018—necessitated a comprehensive modernization program to extend their operational lifespan.

Incremental upgrades began with the installation of the Exocet MM40 Block 3 anti-ship missile—delivered to KRI Bung Tomo in March 2024—expanding its strike envelope to 180 kilometres and introducing limited land-attack capability.

A live-fire trial in August 2023 saw KRI John Lie successfully destroy a decommissioned target vessel, validating the frigate’s enhanced precision-strike capability and affirming the platform’s relevance to contemporary maritime warfare requirements.

These improvements paved the way for a broader mid-life upgrade package, spearheaded by the refit of KRI Usman Harun beginning in 2020 under a bilateral defence agreement endorsed during the Dutch royal visit.

TECHNICAL SPECIFICATIONS: MULTI-ROLE FRIGATES OPTIMIZED FOR INDONESIA’S MARITIME REALITIES

The Bung Tomo-class is based on the versatile Yarrow F2000 design, engineered to provide a compact yet powerful multi-role maritime combatant optimized for littoral, EEZ, and open-sea operations.

Each frigate has a standard displacement of 1,940 tons (2,400 tons full load), measuring 95 meters in length, 13.4 meters in beam, and a 4.6-meter draught—dimensions that enable manoeuvrability in Indonesia’s narrow straits and dense archipelagic waters.

The propulsion architecture consists of four MAN B&W/Ruston 12RK270TC diesel engines delivering 30.2 MW of power, enabling a top speed of up to 30 knots with an operational range of 4,500 nautical miles at 15 knots—sufficient for multi-week patrol missions across Indonesia’s vast maritime expanse.

A standard complement of 107 personnel operates the vessel, supported by automation technologies designed to reduce operator workload and enhance survivability through streamlined damage control processes.

The frigates’ armament suite includes the Oto Melara 76mm/62 Super Rapid naval gun, capable of firing 120 rounds per minute with an effective range of 16 kilometres, supporting both anti-air and anti-surface engagements.

The offensive firepower is anchored by two quadruple Exocet MM40 anti-ship missile launchers—upgraded from Block II to Block 3 variants—featuring 165 kg warheads and advanced sea-skimming trajectories designed to evade radar-based defences.

Defensive systems include two 30mm remotely operated weapon stations, triple 324mm torpedo tubes launching MU90 Impact lightweight torpedoes, and a helicopter deck and hangar capable of supporting AS565 Panther or similar medium-lift helicopters for extended surveillance and ASW missions.

The ships’ original sensor suite featured the Thales Scout surface radar, Kelvin Hughes SharpEye navigation radar, and the TMS 4130C1 hull-mounted sonar, complemented by chaff and towed torpedo decoy systems for layered survivability.

Strategically, the Bung Tomo-class occupies a middle tier between Indonesia’s lighter 1,700-ton Sigma-class corvettes and heavier 2,500-ton Martadinata-class frigates, providing a flexible platform capable of escort operations, exclusive economic zone enforcement, and independent long-duration deployments.

However, aging propulsion systems, outdated software, and obsolescent weaponry underscored the pressing need for a systematic modernization effort that aligns with Indonesia’s evolving maritime strategy.

THE MODERNIZATION PROGRAM: ADVANCED SENSORS, NEXT-GEN WEAPONS, AND NETWORK-CENTRIC WARFARE

The 2025 modernization program for KRI Bung Tomo and KRI John Lie builds directly upon the blueprint established during the refit of KRI Usman Harun, conducted at PT PAL’s Surabaya shipyard but delayed due to global supply chain disruptions.

Part of Indonesia’s R41 refurbishment initiative—which targets 41 naval platforms for life-extension and capability renewal—the upgrade incorporates a series of future-proofed technologies designed for network-centric maritime operations.

Nevesbu leads the engineering phase, deploying 3D laser scanning to map structural wear, analyse hull integrity, and recommend reinforcements essential for operating in high-humidity tropical marine conditions.

Thales Netherlands is responsible for integrating the advanced TACTICOS Combat Management System (CMS), a modular and scalable architecture capable of aggregating sensor data, orchestrating multi-domain engagements, and enhancing decision-making under high-intensity operational conditions.

The modernization introduces cutting-edge sensors, including the SMART-S Mk2 3D air and surface surveillance radar with a detection range of up to 360 kilometres, providing robust situational awareness against low-flying aircraft, UAVs, and surface threats.

Fire control will be improved through the STIR 1.2 EO Mk2 system, while the inclusion of the Vigile Mk2 ESM suite strengthens electronic warfare capabilities, enabling the frigates to detect, classify, and counter hostile emitters in dense electromagnetic environments.

The aging Seawolf SAM system will be replaced by the VL Mica vertical-launch surface-to-air missile system, offering intercept capability against aircraft and incoming missiles at ranges of up to 20 kilometres, marking a significant leap in point-defence capability.

The upgrades will also standardize the Exocet MM40 Block 3 across all three frigates—part of the 2023 PT PAL-MBDA agreement—and incorporate lightweight Black Scorpion mini-torpedoes to enhance anti-submarine warfare performance.

Propulsion improvements may include efficiency enhancements, vibration reduction measures, and overhauled components to improve endurance and lower lifecycle maintenance costs.

PT Len Industri plays a crucial role in local integration, advancing Indonesia’s ambition to expand domestic defence-industrial capacity under MEF’s self-reliance pillar.

The entire modernization project is slated for completion between 2027 and 2028, allowing the ships to remain available for multinational operations such as the Arabian Sea’s Exercise Aman, in which KRI Bung Tomo participated in February 2025.

STRATEGIC IMPLICATIONS: REINFORCING INDONESIA’S MARITIME DETERRENCE IN THE INDO-PACIFIC

The upgrade of the Bung Tomo-class frigates marks a decisive step toward enhancing Indonesia’s maritime deterrence in an increasingly contested Indo-Pacific security environment.

These improvements significantly expand TNI-AL’s ability to project maritime presence, deter incursions into the Natuna Sea, and respond rapidly to grey-zone activities conducted by non-state and state-sponsored actors.

With enhanced anti-submarine warfare capabilities, the modernized ships will counter the proliferation of submarines in regional navies, including China, Vietnam, Singapore, and Australia.

Interoperability enhancements—driven by the TACTICOS CMS and Link Y Mk2 data links—enable seamless integration with allied navies during multinational exercises, strengthening Indonesia’s defence diplomacy with key partners such as India, Japan, and the United States.

Economically, the project supports Indonesia’s domestic defence industry, with PT PAL and PT Len Industri positioned to achieve 60% local content in naval platform production by 2029, an ambition aligned with Jakarta’s long-term naval self-sufficiency goals.

Environmentally, propulsion optimization is expected to reduce emissions and support Indonesia’s commitments under ASEAN’s maritime sustainability framework.

However, challenges remain, including limited budget allocations—just USD 1.32 billion (MYR 6.2 billion) earmarked for the Navy in 2025—and the risks associated with operating a diverse fleet reliant on French, Italian, British, Dutch, and Turkish systems.

Despite these hurdles, Indonesia is projected to operate a balanced fleet of at least 10 frigates and 26 corvettes by 2030, positioning the TNI-AL as one of Southeast Asia’s most capable maritime forces.

CONCLUSION

Indonesia’s decision to modernize KRI Bung Tomo and KRI John Lie represents a sophisticated and pragmatic evolution of its maritime defence strategy, ensuring that proven platforms continue to deliver credible capability in a region defined by escalating competition, strategic ambiguity, and rapid military modernization.

As Indonesia navigates emerging challenges—from grey-zone coercion to climate-induced maritime instability—these upgraded frigates will serve as indispensable assets in defending national sovereignty, safeguarding maritime trade routes, and reinforcing Indonesia’s posture as a stabilizing force in the Indo-Pacific.

With the MEF doctrine gaining renewed momentum under President Prabowo Subianto, the Indonesian Navy stands poised to enter a new era of enhanced readiness, operational flexibility, and strategic relevance.

These modernization efforts also reinforce Jakarta’s long-term ambition to reduce dependence on foreign suppliers by broadening the technological competencies of PT PAL and PT Len Industri through sustained exposure to advanced naval engineering and systems integration.

The upgraded Bung Tomo-class frigates strengthen Indonesia’s ability to maintain credible presence operations in the Natuna Sea, where the convergence of Chinese, Vietnamese, and Malaysian maritime claims continues to stress the regional security architecture.

The integration of network-centric warfare capabilities, including the TACTICOS CMS and Link Y Mk2, provides TNI-AL with the digital backbone required to synchronize real-time intelligence across platforms ranging from submarines to maritime patrol aircraft, thereby amplifying the deterrent value of Indonesia’s distributed naval assets.

The frigates’ enhanced ASW and electronic warfare suites will allow Indonesia to better counter the rapid increase in submarine deployments in the region, particularly as several ASEAN navies—including Vietnam, Singapore, and Thailand—expand their undersea warfare portfolios.

These upgrades also strengthen Indonesia’s capacity to support multinational operations with partners such as Japan, Australia, India, and the United States, reinforcing the country’s role as a central maritime actor within the emerging Indo-Pacific security framework.

The modernization ensures that TNI-AL can respond effectively to both high-intensity conflict scenarios and humanitarian crises, reflecting a dual-purpose approach that aligns military modernization with national resilience priorities in an era of increasingly severe climatic disruptions.

The decision to prioritize mid-life upgrades over immediate new-build acquisitions demonstrates Indonesia’s pragmatic assessment of fiscal realities, emphasizing value maximization, fleet lifecycle extension, and incremental capability growth in a constrained budget environment.

In the broader context of Southeast Asian naval modernization, Indonesia’s revitalized Bung Tomo-class frigates stand as critical symbols of national intent and strategic resolve, highlighting the country’s determination to protect its maritime sovereignty while shaping the strategic equilibrium of the Indo-Pacific.

— DEFENCE SECURITY ASIA