Stealth in the deep: the saga of French submarines

Published on :

24 March 2025
A pioneer in submarine navigation, France opted for nuclear propulsion over half a century ago. A look back at the rich history and latest developments of this highly strategic fleet with Rear Admiral François Guichard, a submarine expert and practitioner.
Le sous-marin nucléaire lanceur d’engins (SNLE) le Triomphant | Lundis de l'IHEDN Furtivité dans les abysses : l’épopée des sous-marins français

Once underwater, man is barely visible to his fellow creatures, and almost completely silent. These qualities, invaluable in times of conflict, have not escaped the notice of the most ancient strategists. "The first known traces of submarine warfare date back to Alexander the Great, when he submerged caissons to build a dyke during the siege of Tyre in 332 BC," explains Rear Admiral (2S) François Guichard, who since summer 2024 has been the first admiral in charge of the French Navy's history function (ALHIST).

This former commander of the nuclear attack submarine (SNA) Amethyst and the nuclear-powered ballistic missile submarine (SNLE) the Terrible is passionate about the history of these technological jewels, which has inspired him to write two novels. "For a long time, people have been interested in the submarine dimension, to wage war or simply to salvage cannons, which were very expensive, from sunken ships", he recounts. In 1472, for example, "a Venetian proposed the plans for a submarine to the doge of the time", who did not follow up.

In the XVIIn the 19th century, "underwater bells" made it possible to walk underwater. And before long, when submarines did not yet exist, "people were already writing about their strategic advantages", says Admiral Guichard with amusement. He mentions the British clergyman and polymath John Wilkins who, in 1648, listed five of them: discretion, safety, the ability to undermine an enemy fleet, to attack or supply discreetly and, finally, to explore the seabed.

IN 1778, THE IDEA OF SAILING UP THE THAMES TO DESTROY THE ENGLISH FLEET

In 1778, when France was at war with England, a courtier, Monsieur Beaugenet, wrote to King Louis XVI proposing a daring offensive: a submarine would sail up the Thames to reach Albion's ships and blow them up. The first "pocket submarine", named American Turtlewas born in 1775 on the other side of the Atlantic.

In 1863, during the American Civil War, the Hunley was the first submarine to sink an enemy vessel, but it sank shortly afterwards. Launched by France the same year, the DiverWith a length of 42.5 metres, she had stability problems (the bow tended to dive) and was decommissioned in 1867. Jules Verne drew inspiration from it for the famous Nautilus of "Twenty Thousand Leagues Under the Sea", published in 1869.

In 1888, Spain and France launched the first electrically-powered submarines. Built at the Toulon arsenal, the French submarine was called the GymnoteIt was 17 metres long and carried a crew of 5. During trials in 1890, it managed to dive under the keel of a ship without being detected, thus forcing a blockade.

In 1899, "the Narwhal represents a first technological breakthrough by combining electric and steam engines, which gives her great length", says Admiral Guichard. "This meant that she took 3 to 5 days at sea, compared with around ten hours at sea. And, adds the officer, "in 1905, France had more submarines than all the other nations of the world put together, while Germany had none".

1914-18: FIRST LARGE-SCALE USE OF SUBMARINES

The First World War saw "the first large-scale use of submarines", particularly during the First Battle of the Atlantic, which the Germans lost. In the 1930s, the Germans invested massively in their submarine fleet. "Submarines could be built quickly and cost less than a large battleship," explains François Guichard.

During the Second World War, this large armada of "U-Boats" from IIIReich" enabled them to avoid the enemy blockade while attacking enemy ships to hinder the supply of their colonial empires. The Germans also failed to win this second Battle of the Atlantic, which played a major role in the war. 

In the Pacific, the opposite was true: Japan, an Axis power alongside Nazi Germany, was subjected to a devastating blockade by American submarines. Although a Japanese submarine managed to bomb Los Angeles on 23 February 1942, it was mainly American submarines that were strangling the Eastern Empire by attacking its supplies.

Four days earlier, on the other side of the continent, the world's largest submarine accidentally sank in the Caribbean Sea. Built in Cherbourg and launched in 1934, the Surcouf (110 metres long, crew of 126) was French and carried a seaplane with folding wings propelled by a catapult. "It was very innovative, even if it only dived to a depth of 80 metres", says Admiral Guichard.

AT THE END OF 1971, THE FIRST FRENCH SNLE WENT INTO SERVICE

On 27 November 1942, the Vichy government ordered the scuttling of the French fleet anchored at Toulon to prevent it falling into the hands of the Reich, which had just invaded the free zone. The crews of four submarines ignored the order, three of them managing to reach the Allies with their ships.

In the post-war period, French submarines were still powered by a diesel-electric combination, which meant that they had to approach the surface regularly to draw in air through a schnorchel (periscope air tube). François Guichard began his career on a conventional vessel like this.

The revolution arrives on 1er December 1971, when the SNLE le Redoubtabledeveloped since the 1950s, is entering active service. French submariners can feel the difference: "A diesel submarine sails at 10 knots on the surface and 5 to 10 knots underwater," explains Admiral Guichard. "With nuclear propulsion, the ratio is reversed, with more than 20 knots underwater.

The 6 Redoutable class SNLEs will serve until 2008. The current class, the Triumphant (138 metres long, with a crew of 112), comprises 4, which provide the oceanic component of France's nuclear deterrent forces (in addition to the air component). The lead ship entered service in 1997, and this class will be replaced from 2035 by 4 SNLE of 3th generation.

THE MULTIPLE MISSIONS OF CONTEMPORARY SNA

The first French SNA, the Rubywas operational in 1981. A total of six ships of this class will be built, three of which are still in service. Naval Group's Barracuda programme, for which François Guichard was responsible on the French Navy side, aims to replace them. The first, the SuffrenThe Suffren class has been in operation since June 2022. The Suffren class ships are 99.5 metres long and carry a crew of 63, fewer than the Rubis class (70), thanks to improved automation.

Admiral Guichard explains that a contemporary SNA has many functions:

"It can fulfil missions at the top or bottom of the spectrum: anti-ship, anti-submarine, launch torpedoes, protect SSBNs or our convoys, threaten enemy convoys, train SSBNs, structure submarine forces, lay mines, launch missiles closer to the coast to destroy land-based infrastructures, deploy commandos or mini-submarines, gather intelligence using its own sensors or by launching drones.

An SNA also serves as part of the aircraft carrier's carrier battle group. Charles de GaulleFrançois Guichard goes on to say that "its missions are not limited".

SNLE: GREAT FREEDOM OF ACTION, GREAT RESPONSIBILITY

As for today's SNLEs, "they are a bit like SNAs, but more discreet, with the added capability of deterrence":

"Each submarine carries the equivalent of 16 Ariane rockets. These sea-to-ground strategic ballistic missiles start their trajectory in the water, then pass into the atmosphere and then into space, capable of flying over the International Space Station, where they would drop their payload. Capable of travelling several thousand kilometres in less than 25 minutes, they offer great freedom of action, which obviously comes with great responsibility.

With these two types of submarine, which have almost infinite autonomy thanks to their nuclear propulsion, "the only limit is human", continues the officer. He himself has already dived 78 days in a row on board an SSBN, and 58 days in an ANS. An SSBN, whose strategic role requires greater autonomy, is equipped to last, without surfacing, 120 days "on normal provisions, and even more on survival". In total, the admiral-writer has logged 28,000 hours diving, or "3 and a half years".

To what depth? This information is classified. "More than 300 metres for both types," concedes François Guichard. According to open source information, an SSBN could reach a depth of at least 400 metres.

Find out more about the origins of French submarines in two historical novels by Rear Admiral François Guichard:

  • "Premières plongées - Vingt milles nautiques sous la mer", 384 pages, published by Locus Solus, 2022 (about the history of the Diver under the Second Empire).
  • "Premières armes - L'appel du large", 416 pages, published by Locus Solus, 2024 (continuation of the previous edition, set in the 1900s).

The nuclear-powered ballistic missile submarine (SNLE) the Triumphantone of four currently in service with the French Navy. Sarah Lacarrère/Marine nationale

Photo credit: The nuclear-powered ballistic missile submarine (SNLE) the Triumphantone of four currently in service with the French Navy. Sarah Lacarrère/Marine nationale