Le Tonnant 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 92.3 metres (302 ft 10 in) long and 8.1 metres (26 ft 7 in) in beam and had a draft of 4.4 metres (14 ft 5 in). They could dive to a depth of 80 metres (262 ft). They displaced 1,572 tonnes (1,547 long tons) on the surface and 2,082 tonnes (2,049 long tons) underwater. Propelled on the surface by two diesel engines producing a combined 6,000 horsepower (4,474 kW), they had a maximum speed of 18.6 knots (34.4 km/h; 21.4 mph). When submerged, their two electric motors produced a combined 2,250 horsepower (1,678 kW) and allowed them to reach 10 knots (19 km/h; 12 mph). Also called "deep-cruising submarines", their range on the surface was 10,000 nautical miles (19,000 km; 12,000 mi) at 10 knots (19 km/h; 12 mph). Underwater, they could travel 100 nautical miles (190 km; 120 mi) at 5 knots (9.3 km/h; 5.8 mph).
In 1937, the French Navy decided that Le Tonnant and her sister shipLe Conquérant would make an extended cruise to Southeast Asia to test the endurance of French submariners and their equipment.[3] Prior to their departure, an incident occurred on board Le Tonnant while she was conducting diesel engine tests at La Seyne-sur-Mer in which two members of her crew plotted to seize control of her and deliver her to the Spanish Republican Navy for service in the Spanish Civil War.[3] Their attempt to take control of Le Tonnant failed and the two ringleaders were imprisoned.[3]
Le Tonnant made her endurance cruise to Southeast Asia in 1938, and from 1 April 1938 she was based in French Indochina,[3] where Le Conquérant joined her in May 1938.[4] Their stay in French Indochina ended in October 1938[3][4] and they returned to Toulon, France, which they both reached on 15 December 1938.[3][4]
In March 1940, Le Tonnant and Le Glorieux participated in a search for a disabled British cargo ship, SS Hartismere, which had suffered machinery damage.[3] On 11 April 1940, Le Tonnant, Le Glorieux, and Le Conquérant took part in exercises off Dakar with the Royal Navy destroyer HMS Decoy.[2] Later in April, Le Tonnant moved to Casablanca, then to Oran.[3]
German ground forces advanced into France, beginning the Battle of France, on 10 May 1940, and that month Le Tonnant moved to Bizerte in Tunisia.[3]Italy declared war on France on 10 June 1940 and joined the invasion, and that day Le Tonnant departed Bizerte to patrol off Cap Bon on the coast of Tunisia.[3] From 20 June she patrolled off Les Salins d'Hyères to protect Toulon.[6] On 24 June, she and her sister ships Fresnel and Pascal were sent to patrol south of Sardinia.[3] The Battle of France ended in France's defeat and an armistice with Germany and Italy that went into effect on 25 June 1940, interrupting their patrols off Sardinia.[3]
Vichy France
After France's surrender, Le Tonnant served in the naval forces of Vichy France, initially in the 1st Submarine Division at Toulon with Le Conquérant, Le Héros, and Le Glorieux.[3] On 17 August 1940, she was disarmed and defueled at Toulon in accordance with the terms of the 1940 armistice.[3]
Le Tonnant was rearmed on 8 April 1941 and subsequently deployed to Casablanca in July 1941 and to Dakar in November 1941.[3] By August or September 1942, according to different sources, she was operating from Casablanca along with Le Conquérant.[3][7] As of 1 November 1942, she was part of the 4th Submarine Division at Casablanca with Le Conquérant, soon joined by their sister ship Sidi Ferruch.[3][7] On 6 November 1942, she was floated out of drydock at Casablanca after a minor refit.[3]
After embarking 10 volunteers from other submarines — nine of them from the submarine Amphitrite — to flesh out her crew, Le Tonnant got underway at 18:35 on 8 November 1942 with only four torpedoes aboard in an attempt to reach Toulon or a neutral port or, if she failed in that, to scuttle herself to avoid capture.[3] Heading north along the coast of French Morocco, she passed El Hank and Fedala between 9 and 10 November 1942. then headed back toward Casablanca.[3] At 08:50 on 10 November, she detected a United States Navytask force north of Casablanca and launched all four of her torpedoes at Ranger, which avoided them.[3]Ranger′s escorts counterattacked and subjected her to a depth-charging, but inflicted no damage on her.[3] At 12:25, a U.S. Navy PBY Catalina bombed and damaged her.[3]
Unable to return to Casablanca, Le Tonnant proceeded to Cádiz in neutral Spain, arriving there on 14 November 1942.[3] Deciding that Le Tonnant could not make it to Toulon, her executive officer, still in command, decided to scuttle her.[3] After disembarking 45 crew members at Cádiz, Le Tonnant got underway with a skeleton crew on board consisting of her executive officer and five others.[3] After she reached the open sea, her executive officer opened her seacocks at 12:02 on 15 November 1942 and Le Tonnant sank.[3][2][9] All six men on board abandoned ship, and a Spanish trawler rescued them.[3]
Fontenoy, Paul E. (2007). Submarines: An Illustrated History of Their Impact (Weapons and Warfare). Santa Barbara, California. ISBN978-1-85367-623-9.((cite book)): CS1 maint: location missing publisher (link)[verification needed]
Gardiner, Robert; Chesneau, Roger (1980). Conway's All the World's Fighting Ships 1922–1946. London: Conway Maritime Press. ISBN0-85177-146-7.
Huan, Claude (2004). Les Sous-marins français 1918–1945 (in French). Rennes: Marines Éditions. ISBN9782915379075.
Picard, Claude (2006). Les Sous-marins de 1 500 tonnes (in French). Rennes: Marines Éditions. ISBN2-915379-55-6.
France
