Belgium donates last four Tripartite-class minehunters to Bulgaria to secure Black Sea naval routes.

On September 12, 2025, Belgium’s Council of Ministers approved the transfer of its four remaining Tripartite-class minehunters to Bulgaria at no purchase cost, with Sofia to fund restoration and modernization in Belgian industry. The decision fits a broader push to reinforce Black Sea mine countermeasures and to align replacement timelines as Belgium and the Netherlands field their next-generation rMCM (Replacement Mine CounterMeasure) fleet later this year. Officials have also framed the package to include spare parts and a tactical simulator so the ships join Bulgaria as usable operational assets rather than simple second-hand hulls.
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The four Belgian Tripartite-class minehunters set to join Bulgaria are BNS Bellis (M916), BNS Crocus (M917), BNS Lobelia (M921), and BNS Primula (M924), commissioned between 1986 and 1991. (Picture source: Facebook/M924 Primula)

The Belgian decision sits inside a trilateral construct in which the Netherlands has signaled it will add three Alkmaar-class ships, with administrative and technical work underway toward a memorandum of understanding among the three governments. Bulgaria will finance the commissioning and longer-term maintenance of the donated Belgian vessels, largely through Belgian operators and activities, and can use existing defense agreements or new procurement actions to do so. Public briefings describe a package that explicitly includes spares and a simulator, while the broader objective is to create a coherent, larger Black Sea mine countermeasures flotilla based on one class of ship. The planned arrangement also foresees Bulgarian support to regional partners through training and coaching on the type, linking the transfer to wider assistance connected to the war in Ukraine.

Ukraine has received two Tripartite-class minehunters so far: the Belgian ship Narcis (M923) transferred in June 2025 and renamed Mariupol, and the Dutch ship Vlaardingen (M863) transferred at the same time and renamed Melitopol. A third vessel, the former Dutch minehunter Makkum (M857), has also been pledged to Ukraine and will be renamed Henichesk when the transfer occurs. Before handover, all three ships underwent periods of maintenance and crew training with Belgian and Dutch instructors to ensure they meet operational standards. Ukraine acquired these minehunters to address the threats posed by naval mines and underwater explosive devices along its Black Sea coast, key shipping lanes, and approaches to major ports such as Odesa, which are vital for Ukraine’s economy and export of agricultural goods. The ships are intended to strengthen Ukraine’s capacity to detect, classify, and neutralize mines, especially in shallower and coastal waters where fixed and drifting mines pose the highest risk. Furthermore, Bulgaria has agreed to provide assistance services to Ukraine in the form of training and crew preparation.

Sofia’s experience with the Tripartite-class began with ex-Belgian M922 Myosotis, withdrawn in the mid-2000s and sold to Bulgaria, where it entered service after overhaul as BGS Tsibar with board number 32 as part of a 2009 package with two second-hand Wielingen-class frigates reported at more than 50 million euros. A decade later, Bulgaria approved the acquisition of two ex-Dutch Alkmaar-class ships, the former Maassluis and Hellevoetsluis, inducted at Varna on October 14, 2020, as BGS Mesta and BGS Struma with board numbers 31 and 33. The Dutch pair’s purchase price was reported to be around 2.4 million euros for both hulls, with Bulgarian sources citing additional outlays of about 4.69 million BGN for acquisition and a further 3.92 million BGN for reactivation and transport in 2020. By 2025, Bulgaria had expressed interest in the remaining Belgian and Dutch Tripartite ships due to persistent mine risks in the western Black Sea. The new Belgian donation adds four hulls, with a €24 million restoration and modernization contract placed with Belgian companies to return them to full operational status and to build a sustainment pipeline for the enlarged fleet.

The four Belgian Tripartite-class minehunters set to join Bulgaria are BNS Bellis (M916), BNS Crocus (M917), BNS Lobelia (M921), and BNS Primula (M924), and all were built at the Béliard Shipyard in Ostend. Bellis, laid down in 1984 and commissioned in August 1986, has served in NATO mine countermeasure groups and took part in operations in the North Sea and Baltic. Crocus, launched in 1986 and in service from July 1987, was briefly modified in 1988 with a Milan missile launcher during a Gulf mission and has since rotated through various NATO deployments. Lobelia, commissioned in July 1989, underwent upgrades in the 2000s and continued service from Zeebrugge while regularly participating in allied exercises. Primula, the youngest of the group, was commissioned in May 1991 and similarly upgraded with modern sonar and combat systems, serving in Belgian waters and international minehunting operations until its planned withdrawal. Each carries the typical characteristics of the Belgian “Flower class,” being named after flowers and configured with Atlas Elektronik IMCMS combat data systems and minehunting equipment compatible with NATO standards. They all underwent upgrades in the 2000s, receiving the same sonar package as their French counterparts and improved propulsion systems.

The Tripartite-class minehunter originated from a multinational naval program that began in the early 1970s when Belgium, France, and the Netherlands identified a common requirement for modern mine countermeasure vessels. A cooperation agreement was signed on 9 December 1974 by the three navies’ chiefs of staff to produce a standardized ship with shared systems but national construction lines. The program initially planned for 60 hulls, of which 40 were completed and 20 were cancelled as requirements shifted. France provided the minehunting and electronic systems, the Netherlands developed propulsion systems, and Belgium was responsible for minehunting propulsion and electrical generation. Production ran between 1977 and 1995, with the first ships entering service in 1983. Belgium ordered ten ships with an option for five more that was never activated, France reduced its order to ten for budgetary reasons, and the Netherlands ordered fifteen. These ships later became the basis for exports and transfers, with additional navies integrating them into their fleets, while Belgium, France, and the Netherlands pursued replacement programs with rMCM and SLAM-F designs.

The design of the Tripartite-class emphasized reducing signatures and ensuring precise maneuverability during minehunting operations. The ships were constructed with glass-reinforced plastic hulls to lower magnetic and acoustic signatures, a feature that significantly reduced vulnerability in mined waters. For propulsion, the vessels combined a 1,400-kilowatt Brons-Werkspoor or Wärtsilä diesel engine driving a controllable pitch propeller for transit with auxiliary systems comprising two ACEC active rudders and a bow thruster. These auxiliary systems, powered by Turbomeca Astazou IVB gas turbine alternators or diesel alternators, enabled highly controlled, low-speed maneuvering required for minehunting, with speeds of around 7 knots. The ships carried hull-mounted sonar such as the DUBM-21B, later replaced by the TSM 2022 Mk III during refits, to detect and classify mines. They also deployed remotely operated vehicles such as the ECA PAP-104, and in later modernizations, Seafox or Double Eagle systems, for mine identification and disposal. A soundproofed control room integrated sonar, navigation radars such as the Decca 1229 or Bridgemaster E250, and combat data systems like Atlas Elektronik IMCMS, while deck arrangements allowed the embarkation of clearance divers with a decompression chamber if required.

The general characteristics of the Tripartite-class varied slightly among French, Dutch, and Belgian variants. The vessels measured about 51.5 to 51.6 meters in length, with a beam of approximately 8.9 to 8.96 meters and a draught of 3.6 to 3.8 meters. Displacement ranged from 536 tonnes standard to 605 tonnes at full load, later increasing in some refitted versions to around 625 tonnes. In transit mode, powered by the main diesel engine, they reached speeds of up to 15 knots with a range of about 3,000 nautical miles at 12 knots. Minehunting propulsion systems allowed speeds of around 7 knots with high maneuverability, supported by autopilot and automatic position control systems. Standard equipment included hull-mounted sonar, navigation radars, mine disposal systems, and remotely operated vehicles. Belgian ships, following upgrades between 2004 and 2008, were aligned with French specifications by replacing earlier anti-mine warfare equipment with the TSM 2022 sonar, Atlas Elektronik IMCMS combat data system, and Seafox drones. Armament across the class remained light, intended for self-defense only, with a French fit of a 20 mm modèle F2 gun, and Belgian and Dutch ships generally mounting three 12.7 mm machine guns, supplemented in some cases by 7.62 mm weapons. Crews typically ranged from 33 to 55, depending on mission profiles and modernization status.

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, 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.