Achéron was part of a fairly homogeneous series of 31 deep-sea patrol submarines also called "1,500-tonners" because of their displacement. All entered service between 1931 and 1939.
The Redoutable-class submarines were 92.3m (302.8feet) long and 8.1m (26.6feet) in beam and had a draft of 4.4m (14.4feet). They could dive to a depth of 80m (260feet). They displaced 1572t on the surface and 2082t underwater. Propelled on the surface by two diesel engines producing a combined 6000hp, they had a maximum speed of . When submerged, their two electric motors produced a combined 2250hp and allowed them to reach . Also called "deep-cruising submarines", their range on the surface was at . Underwater, they could travel at .
Laid down at Ateliers et Chantiers de la Loire in Saint-Nazaire, France, on 4[1] or 24 September 1927 with the hull number Q150, Achéron was launched on 6 August 1929.[1] She was commissioned on 22 February 1932.[1]
In 1937, Achéron received orders to make a cruise to Argentina in company with her sister ships,, and .[2]
At the start of World War II in September 1939, Achéron was assigned to the 3rd Submarine Division in the 2nd Squadron — a component of the 1st Flotilla — based at Toulon, France.[2] Her sister ships, Fresnel, and made up the rest of the division.[2] [3] In December 1939, Achéron joined Fresnel and their sister ships and in searching the central Atlantic Ocean for the German supply ship .[2] [4] Agosta and Béveziers, which were returning to France from the French West Indies, also joined in the search.[2]
At the beginning of February 1940, the 3rd Submarine Division transferred briefly to Casablanca in French Morocco and on 6 February 1940 began patrols off the Canary Islands, where the Allies believed that German cargo ships[2] had taken refuge at the beginning of the war and were serving as supply ships for German U-boats. During these patrols, Achéron opened fire with her deck gun on a 5,265-gross register ton steam cargo ship that her crew suspected of being a German blockade runner, forcing the ship to stop in the Atlantic Ocean at 34.4167°N -26°W.[2] Crewmen from Achéron boarded the ship and determined that she was the British merchant ship,[2] after which Achéron allowed her to proceed.
On 12 April 1940, the 3rd Submarine Division was transferred to the Mediterranean Sea, based first at Bizerte in Tunisia. While Fresnel remained at Bizerte, the division′s other submarines then transferred to Beirut in the French Mandate for Syria and Lebanon, from which they operated under the command of the British Commander-in-Chief, Mediterranean Fleet, Admiral Andrew Cunningham at Alexandria, Egypt.[2] [5] Achéron patrolled in the Eastern Mediterranean in the approaches to Beirut.
German ground forces advanced into France on 10 May 1940, beginning the Battle of France, and Italy declared war on France on 10 June 1940 and joined the invasion. On the day Italy entered the war, British submarines based at Beirut departed for operations in the Aegean Sea off the Dardanelles and in the Tobruk area off the coast of Libya, and on 11 June the French submarines,, and also departed to operate in the Dodecanese, leaving only Achéron to defend the approaches to Beirut.[2] On 16 June 1940, an Italian torpedo boat fired a torpedo at Achéron, but missed.[2]
The Battle of France ended in France's defeat and armistices with Germany on 22 June 1940 and with Italy on 24 June, both of which went into effect on 25 June 1940. Achéron — by then assigned to the 3rd Submarine Division in the 3rd Squadron in the 1st Flotilla[2] — was recalled to Beirut.[6]
After France's surrender, Achéron served in the naval forces of Vichy France. Her batteries and those of her sister ship — which also was at Beirut — were in poor condition, but repairing or replacing them was impossible at Beirut.[7] Escorted by the netlayer, the two submarines departed Beirut on 16 October 1940 bound for Toulon, which they reached on 24 October 1940.[2] [7] At Toulon, Achéron was placed under guard and maintained in a disarmed and unfueled state in accordance with the terms of the Armistice of 22 June 1940.[8] By 1 November 1942, still in this status at Toulon, Achéron had been assigned to the 1st Submarine Group along with her sister ships,, and .[2]
Achéron was at Toulon when Germany and Italy occupied the Free Zone (French: Zone libre) of Vichy France on 27 November 1942, and she was among the French vessels scuttled at Toulon to prevent their seizure by Germany when German forces entered the naval base that day,[1] [9] sinking in Dock No. 3 of the Vauban Grand Docks.[2]
The Germans seized Achéron and handed her over to the Italians for scrapping.[2] Her wreck lay in a position where her stern hindered the closing of Dock No. 3, so divers cut her stern.[2] [10] The Italians refloated her on 26 June 1943,[1] [2] but she was still at Toulon when Italy surrendered to the Allies on 9 September 1943. The Germans seized her and earmarked her for scrapping, but 88 American bombers dropped 240ST of bombs on the Toulon Arsenal and sank her on 24 November 1943 before she could be scrapped.[1] [11]