Belgium seeks new frigate builders as Dutch ASWF partnership faces soaring costs and seven-year delay.

Belgian Defence Minister Theo Francken announced on July 19, 2026, that Belgium will launch a Request for Information (RFI) to shipbuilders in France, Germany, Italy, Spain, and Türkiye before deciding in October whether to exit the joint Belgian-Dutch Anti-Submarine Warfare Frigate (ASWF) programme. The decision follows cumulative ASWF project delays reaching six years and unit procurement costs escalating from €600 million to over €1.3 billion per vessel. The review aims to determine if an alternative surface combatant can enter service earlier to replace Belgium's aging Karel Doorman-class frigates without compromising NATO North Sea operational requirements.

The Belgian Ministry of Defence issued an RFI after estimated costs for two Belgian ASWF frigates rose from €1.2 billion to over €2.5 billion due to structural design modifications that increased vessel displacement to 6,650 tonnes. Alternative candidate platforms under evaluation include the Italian FREMM, Spanish F110, French FDI, German MEKO variants, and Turkish İstif-class derivatives to prevent an operational gap before the scheduled 2034 retirement of Belgium's current fleet.

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The Belgian-Dutch Anti-Submarine Warfare Frigate (ASWF) programme has experienced cumulative cost increases exceeding 100%, while first deliveries have slipped by approximately six to seven years, from 2027–2028 to 2033–2034. (Picture source: Damen)

On July 19, 2026, Belgian Defence Minister Theo Francken announced that Belgium will launch a Request for Information (RFI) from shipbuilders in France, Germany, Italy, Spain and Türkiye before deciding in October whether to remain in the Belgian-Dutch Anti-Submarine Warfare Frigate (ASWF) programme. The review follows cumulative cost increases exceeding 100% and delivery delays approaching seven years. Belgium initially planned approximately €1.2 billion for two ships, or about €600 million per frigate. The amount approved in 2023 approached €2 billion once weapons, sensors, ammunition, and support were included, while later estimates put the total at €2.5 billion to €2.6 billion before shore infrastructure, additional missile stocks, personnel expansion, long-term maintenance, and a possible third frigate are added.

Delivery has also moved from 2027 to 2028 to 2030 and then to 2033 or 2034. Belgium must now determine whether the ASWF justifies a delay of approximately six years and a unit cost more than twice the original planning figure, or whether another frigate could enter service earlier without reducing the level required for NATO operations in the North Sea and North Atlantic. The Anti-Submarine Warfare Frigate (ASWF) was launched on November 30, 2016, under the Belgian-Dutch naval cooperation agreement. Belgium became responsible for replacing the two countries' mine countermeasure fleets, while the Netherlands assumed responsibility for replacing the four remaining M-class frigates, two Dutch and two Belgian.

This division allowed both navies to avoid parallel development costs and retain common training, logistics, maintenance and operational procedures under the BENESAM cooperation structure. Belgium subsequently ordered six City-class mine countermeasure vessels, while the Netherlands managed the frigate design through the Defence Materiel and IT Command, Damen Naval, Thales and a wider group of European suppliers. Belgian approval in 2023 covered two ASWF frigates with their combat systems, weapons and associated support. Now, at €1.3 billion per ship, each Belgian ASWF would cost more than twice the approximately €600 million figure used during the earlier planning phase. Belgium would also have to finance at least two complete crews, shore training, simulators, maintenance facilities, spare parts, torpedoes, surface-to-air missiles and anti-ship missiles.

A third frigate, required for a sustainable force-generation cycle, could raise the long-term surface combatant investment above €3.8 billion before lifetime operating costs. Belgium's current naval force leaves little margin for additional delay. The Leopold I and Louise-Marie are former Dutch Karel Doorman-class frigates built in the 1980s, launched in 1988 and 1989 and commissioned by the Netherlands in 1991. Belgium purchased both ships in December 2005, placing Leopold I in service in March 2007 and Louise-Marie in April 2008. Each vessel is approximately 122.3 metres long, 14.4 metres wide and displaces about 2,800 tonnes in the original standard configuration. Their Cold War-era combat fit included sixteen RIM-7 Sea Sparrow missiles, eight Harpoon anti-ship missiles, a 76 mm gun, a Goalkeeper close-in weapon system, twin lightweight torpedo launchers and facilities for one helicopter.

The ships have received modernization work, but their basic machinery, hull structure, electrical architecture and several weapons remain products of a design developed more than 40 years ago. By 2034, Leopold I would be 46 years beyond launch and Louise-Marie 45 years beyond launch. Maintaining them until that date would require repeated propulsion work, structural inspections, replacement of obsolete electronics, and continued management of components no longer supported by their original manufacturers. Their limited electrical reserve and internal volume also restrict the installation of modern radars, electronic warfare systems, vertical-launch weapons, and counter-drone equipment.

A sustainable frigate force normally requires at least three ships to keep one vessel continuously available: one deployed or ready for deployment, one preparing or recovering, and one undergoing maintenance. Belgium has only two. When one ship enters a major maintenance period, the entire national frigate capability depends on the availability of the other. Louise-Marie's planned 2024 deployment to the Red Sea was delayed after operational tests identified several faults, including a malfunction involving a Sea Sparrow missile in its launcher. The ship eventually deployed, but the incident illustrated the operational consequence of ageing equipment in a two-ship fleet. A single launcher, propulsion, or sensor failure can remove 50 percent of nominal frigate strength, while simultaneous maintenance can leave Belgium without an operational frigate.

Extending both vessels beyond 2030 would preserve hull numbers but would not guarantee combat availability. The Navy would also have to retain specialist technicians and sailors for an ageing class while simultaneously training personnel for its replacement, increasing manpower pressure during the transition. The ASWF is substantially larger and more capable than the ships it will replace. The current design is approximately 145 metres long, around 18 metres wide and between 6,400 and 6,650 tonnes at full displacement. Its size is close to that of several European destroyer-sized frigates and more than twice the displacement of the Karel Doorman-class. Propulsion uses a Combined Diesel-Electric and Diesel (CODLAD) arrangement.

Electric motors can propel the ship at submarine-search speeds with less machinery noise than a conventional mechanical drive, while diesel engines provide higher power for transit and escort operations. The machinery includes two MAN 20V28/33D STC propulsion engines and four MAN 16V175D-MEV generator sets connected through RENK gearboxes and an integrated electrical system. The acoustic objective is not simply lower engine noise. Pumps, ventilation, gearboxes, shafts, propellers and auxiliary machinery must also be isolated to reduce radiated noise across the frequency bands detected by modern submarine sonars. The larger hull provides space for machinery separation, raft-mounted equipment, additional fuel, mission systems and reserve electrical capacity, all of which are more difficult to accommodate in a 3,000 or 4,000-ton frigate.

The underwater warfare suite is the central element of the ASWF design. Ultra Maritime's Sea Lancer and Sea Sabre systems combine active and passive low-frequency detection with variable-depth operation, allowing the ship to place its sonar below thermal layers that can mask submarines from hull-mounted sensors. A bow sonar supports short- and medium-range search, while towed arrays improve passive detection against diesel-electric and nuclear-powered submarines. Mine and obstacle avoidance sensors support operations in shallow or confined waters. The ship's sensors are integrated with a Dutch Under Water Warfare System and an Above Water Warfare System intended to fuse radar, sonar, electronic support, electro-optical and weapon data.

Above-water surveillance includes Thales APAR Block 2, an X-band active electronically scanned array radar used for tracking and missile guidance, and the SM400 Block 2 S-band surveillance radar for wider-area air and surface detection. Scout Mk3, Gatekeeper Mk2 and Mirador Mk2 provide passive surveillance, panoramic electro-optical coverage and precision fire control. This combination is intended to support simultaneous submarine prosecution, air defense, surface tracking and drone detection rather than forcing the ship to concentrate on one mission at a time. Two eight-cell Mk41 launch modules provide sixteen cells. When loaded exclusively with quad-packed ESSM Block 2 missiles, the ship could carry up to sixty-four missiles, although the actual load would depend on mission requirements and whether Belgium later integrates larger weapons.

Strike-length cells are physically capable of accepting missiles larger than the ESSM, but weapons such as SM-2, SM-6 or land-attack missiles would require separate software integration, fire control certification, testing and political approval. Surface warfare is based on eight Naval Strike Missiles in two four-canister launchers, for a range above 185 kilometres thanks to an imaging infrared seeker for terminal identification and aim-point selection. Point defense includes a 21-round RAM launcher, one 76 mm OTO Sovraponte gun and two Bofors 40 Mk4 guns. The 76 mm weapon can use guided DART ammunition against aircraft, missiles and unmanned systems, while the 40 mm guns provide a lower-cost engagement option against drones, small boats and short-range aerial targets.

Mk54 lightweight torpedoes, an NH90 NFH helicopter and unmanned aerial or surface vehicles extend the anti-submarine engagement area beyond the ship's own sonar range. The ASWF's delay is closely connected to the expansion of these requirements. The original hull no longer provided sufficient stability and reserve capacity after the addition of heavier sensors, more weapons, unmanned systems, larger electrical loads, additional cooling and future modernization margins. The redesign increased the length by approximately seven metres and beam by about 0.5 metres, while the displacement rose by several hundred tonnes. Therefore, designers had to recalculate longitudinal strength, intact and damaged stability, centre of gravity, shaft alignment, hydrodynamic resistance, compartment arrangements and weight distribution.

Larger missile installations required deck reinforcement, blast protection, ammunition handling changes and additional combat system interfaces. More radar and electronic warfare equipment increased topweight, while larger generators and cooling plants affected machinery spaces and ventilation routes. Requirements for counter-drone systems, future directed energy weapons and operations in northern waters increased power, heating and structural demands. Like the U.S. Constellation-class frigate, the design therefore continued changing while production planning was already under way, delaying the point at which drawings could be frozen, and construction could proceed without further rework. Measured strictly against the original Belgian requirement, the Italian FREMM ASW or FREMM EVO has the highest probability of replacing the ASWF without a major reduction in anti-submarine capability.

These FREMM variants are approximately 144.6 metres long and displace around 6,700 to 6,900 tonnes, placing them within a few hundred tonnes of the ASWF. The CODLAG propulsion allows electric operation during submarine searches. The ASW configuration combines the UMS 4110 hull sonar, CAPTAS-4 variable-depth sonar, MU90 torpedoes, NH90 helicopters and, on some ships, MILAS anti-submarine missiles. Sixteen Sylver A50 cells support Aster 15 and Aster 30 surface-to-air missiles, while two 76 mm guns and anti-ship missiles provide close defense and surface-strike capability. FREMM has the lowest design risk among the principal candidates because more than twenty ships derived from the Franco-Italian programme are in service or under construction/consideration for France, Italy, Egypt, Morocco, Greece, Indonesia and the United States.

Its limitation is that its basic architecture dates from the mid-2000s. It offers less unallocated internal volume and electrical growth than the ASWF, but its propulsion, sonar, endurance and helicopter facilities most closely reproduce the Belgian requirement without requiring a new hull design. Spain's F110 ranks second because it matches the ASWF's length, digital architecture, Mk41 compatibility and general growth potential, but it is less specialized for quiet submarine-hunting operations. The ship is approximately 145 metres long and displaces more than 6,000 tonnes. It uses the SCOMBA combat management system, four fixed SPY-7(V)2 radar arrays, Mk41 vertical-launch cells, hull-mounted sonar, a variable-depth sonar and facilities for an NH90 helicopter.

The class is designed around a digital twin, integrated platform management systems and software-based capability growth, features that could simplify upgrades over a service life extending into the 2060s. Its principal difference from the ASWF is mission priority. The Spanish Navy designed the F110 as a general-purpose escort able to conduct air defense, anti-submarine warfare, surface warfare and maritime security tasks in roughly equal measure. The ASWF concentrates more hull volume, acoustic treatment and sensor architecture on submarine detection. Spain is also constructing five F110s for its own fleet, so Belgium would have to determine whether Navantia could provide an export slot before 2033 without disrupting Spanish deliveries. A Belgian-specific radar, missile or sonar configuration would further increase integration work and could erode the schedule advantage over the ASWF.

The French FDI ranks third because it provides substantial combat capability, but its hull offers less endurance, payload, and modernization reserve. The ship is about 122 metres long and displaces approximately 4,460 tonnes, making it roughly the same length as Belgium's current frigates but more heavily armed and far more automated. Its four-panel Sea Fire S-band AESA radar supports simultaneous surveillance, target tracking and Aster missile guidance. The underwater suite combines KingKlip Mk2 hull sonar and CAPTAS-4 Compact variable-depth sonar, while SETIS manages sensor and weapon data. Depending on configuration, the ship can carry sixteen or thirty-two Sylver cells, Aster 15 or Aster 30 missiles, Exocet MM40 Block 3C anti-ship missiles, MU90 torpedoes and an NH90 helicopter.

A crew of approximately 125 and endurance of up to 45 days indicates a high level of automation for a ship of this size. The main limitation for Belgium is physical reserve. The FDI is more than 2,000 tonnes lighter than the ASWF and has less volume for additional launch cells, unmanned systems, command facilities, electrical generation and directed-energy weapons. It could meet current operational needs, but it would provide less margin for capability growth during a service life likely to exceed 35 years. Germany's MEKO variants could rank near if TKMS proposes a low-risk configuration close to 6,000 tonnes with proven sensors and weapons. The A-200 generally displaces between 3,700 and 4,000 tonnes, while projected A-300 variants approach 5,500 to 6,000 tonnes depending on customer requirements.

The MEKO concept allows the customer to select radar, sonar, propulsion, combat management, electronic warfare and weapons from different suppliers. Belgium could therefore request Mk41 cells, ESSM Block 2, Naval Strike Missile, CAPTAS sonar, an NH90-compatible flight deck and a radar from Thales or another European manufacturer. This flexibility could increase Belgian industrial participation and preserve compatibility with existing NATO ammunition. It would also create engineering risk because the final Belgian configuration would require integration and certification across systems not previously combined on the same hull. A heavily customized MEKO A-300 could approach the ASWF in displacement and weapons, but it would not automatically reproduce its acoustic performance, sonar arrangement or future power margins.

The more Belgium modifies the design, the more the procurement begins to resemble a new development programme rather than the purchase of a mature ship. Türkiye's most likely offer would be an export derivative of the İstif-class through STM, ASFAT or a consortium involving Turkish naval shipyards and combat-system suppliers. However, the İstif class ranks last against the unchanged ASWF requirement because its smaller hull cannot match the Belgian-Dutch design in acoustic discretion, sonar capacity, missile load or future growth. The existing class is approximately 113 metres long and displaces around 3,100 to 3,400 tonnes. It carries vertical-launch cells, Atmaca anti-ship missiles, lightweight torpedoes, an indigenous radar and combat management system, a helicopter and short-range defensive weapons.

Turkish shipyards could offer lower labour costs, shorter construction cycles and broader customer customization than several Western European yards. The design is also compatible with NATO communications and could be adapted to foreign missiles and sensors. Its limitation is not the absence of modern equipment but hull volume. A ship displacing about half as much as the ASWF cannot provide the same fuel load, sonar volume, machinery isolation, electrical generation, missile capacity, damage tolerance, or future growth without being substantially enlarged. An enlarged Turkish derivative could reduce that gap, but once length, displacement, propulsion, and combat systems are changed, the schedule and cost advantage would become less certain.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.

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