On Tuesday, October 28, 2025, France’s General Directorate for Armament (Direction générale de l’Armement, DGA) under the Ministry of the Armed Forces and Veterans announced that on October 24, Minister Catherine Vautrin had signed a decision to equip the strategic submarine Le Téméraire (S617) of the Le Triomphant-class with the newest version of the M51.3 submarine-launched ballistic missile.
Photo: ArianeGroup
As reported, this key milestone marks the completion of the development and testing phase of the M51.3 missile, which began in 2015, and confirms the credibility of France’s naval nuclear deterrent component. The M51.3 was developed as a modernization of the M51.2 by Airbus Defence and Space and Safran (within their joint venture, ArianeGroup), which received the contract in May 2016. The work was expected to conclude in the early 2020s, with operational service entry planned around 2025.
ArianeGroup has been the main industrial contractor for France’s MSBS (Mer-Sol Balistique Stratégique) sea-based ballistic missile program since 2000. The M51 is the successor to the strategic M45 missile and represents the sixth generation after the earlier M1, M2, M20, and M4. Compared with its predecessor, the M51’s overall length was increased from 11.05 to 12 meters, diameter from 1.93 to 2.3 meters, and mass from 35 to 52 tons. The modernized M51.3 features a redesigned third stage that extends its range and improved decoys to better penetrate enemy missile defense systems.
The M45 carried six TN75 thermonuclear warheads with a yield of 110 kT, while its successor, the M51.1, could carry 6–10. The M51.2 received new-generation TNO (Tête nucléaire océanique) warheads with a yield of 150 kT, housed in a reentry vehicle. The missile’s range increased from 6,000 km to 8,000–10,000 km for the M51.1 and up to 11,000 km for the M51.2. The newest M51.3 is expected to have an extended range by several hundred kilometers and improved TNO-2 warheads.
Le Téméraire (S617), along with its sister submarines Le Triomphant (S616), Le Vigilant (S618), and Le Terrible (S619), will serve as interim carriers of the M51.3 until the introduction of a new generation of submarines under the SNLE 3G (Sous-Marin Nucléaire Lanceur d’Engins de 3e Génération) program. The program was launched on February 19, 2021, and the first unit’s steel cutting took place on March 20, 2024. Four submarines are scheduled to enter service between 2035 and 2050, replacing their predecessors at five-year intervals. They will carry out nuclear deterrence patrols until 2090 as part of the ESNA (Escadrille des Sous-Marins Nucléaires d’Attaque) squadron within France’s strategic naval forces, FOST (Force océanique stratégique).
Operational deployment follows a series of successful flight tests, including the final qualification launch conducted on June 12 of this year from Le Téméraire (S617) as part of Operation Aquilon 25. This launch, carried out under operational conditions, confirmed the missile’s performance and its integration with the submarine’s combat system.
This success is the result of teamwork between the DGA, the CEA (Commissariat à l’énergie atomique et aux énergies alternatives), the FOST strategic naval forces, and the defense industry – in particular, ArianeGroup and its subcontractors.
France now possesses a modern and credible naval nuclear deterrent component capable of meeting current and future threats. The introduction of the M51.3 missile strengthens France’s strategic autonomy and contributes to Europe’s security, notes the DGA communique.
Meanwhile, the M51.3 is not the end of the MSBS M51 family’s evolution. On September 12 of this year, ArianeGroup announced that it had received an order from the DGA to develop and produce the next modernization package, designated M51.4. Details have not been disclosed, but it is known that the new variant will feature greater range, precision, and strike capability.
Le vendredi 24 octobre, @CaVautrin a signé la mise en service opérationnel de la troisième version du missile M51, le M51.3. Il s’agit d’une étape majeure dans la modernisation de la composante océanique de la dissuasion nucléaire française.
Équipé de nouvelles têtes nucléaires…
— Ministère des Armées et des Anciens combattants (@Armees_Gouv) October 28, 2025
Ce vendredi 24 octobre, j’ai signé la mise en service opérationnel du missile M51.3, troisième version du missile stratégique M51.
Fruit d’un travail mené par la Direction générale de l’armement (DGA) avec l’État-major des armées, la Marine nationale, le Commissariat à l’énergie…
— Catherine Vautrin (@CaVautrin) October 28, 2025
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