A nuclear-powered ballistic missile submarine (SNLE) of the Strategic Oceanic Force (Fost) conducted a test firing of a strategic ballistic missile, the M51, on Tuesday. The missile did not carry a nuclear warhead. The SNLE Long is 138 meters long and 12.5 meters wide. The Fost is one of two components of France's nuclear deterrence, the other being the Strategic Air Forces (FAS). The Fost ensures that France maintains a second-strike capability, meaning it can retaliate even after a nuclear attack. The test firing came after a period of maintenance known as Iper, which happens every ten years at the L'Ile-Longue base in the Finistère region. This base, located on the Crozon peninsula, employs nearly 2,500 people, both military and civilian, to support the SNLE submarines. During the Iper phase, weapons and nuclear fuel are removed from the submarines, allowing for preventive and corrective maintenance on all systems, especially those related to energy production and propulsion. The four current SNLE submarines of the Le Triomphant class (Le Triomphant, Le Téméraire, Le Vigilant, and Le Terrible) will be gradually replaced by four new SNLE submarines of the L'Invincible class starting in 2037. These third-generation submarines will be larger, with a length between 147 and 150 meters, and will include advanced features such as improved stealth, better detection systems, and reduced magnetic signatures. The first of these new submarines, L'Invincible, is expected to be launched in 2036 and delivered by the end of 2037, with the remaining three units to follow every five years. The SNLE 3G will be responsible for deterrence missions until the end of the 2080s. President Emmanuel Macron commented on Tuesday on the X network, stating that France's nuclear deterrence protects the country and will continue to do so. He referenced the test firing of a M51.3 missile by the SNLE Le Vigilant. According to official doctrine, at least one SNLE submarine should be on patrol at all times. The SNLE have been conducting patrols to ensure the constant presence of nuclear deterrence at sea since 1972. Nuclear-powered attack submarines (SNA) do not carry strategic weapons but are equipped with nuclear propulsion. Their missions include supporting deterrence operations, escorting valuable units, gathering intelligence, and engaging in underwater combat. They can accompany the Charles-de-Gaulle aircraft carrier during its operations. The current SNA of the Suffren class are replacing the older Rubis-class submarines, which were commissioned starting in the 1980s. Three new SNA submarines—Suffren, Duguay-Trouin, and Tourville—have already been commissioned, with another, De Grasse, expected to be commissioned by the end of the year. The last two submarines in the program, Rubis and Casabianca, are currently under construction and are expected to be delivered by 2030. These new SNA submarines are longer than their predecessors and are equipped with more advanced armaments, including torpedo tubes, anti-ship missiles, and cruise missiles. They are also described as faster, more durable, and more versatile than the previous generation.