French submarine Poncelet

On 28 October 1937, one of the sailors in Poncelet′s engineering department suffered an injury.[2]

At the start of World War II in September 1939, Poncelet was assigned to the 6th Submarine Division in the 4th Submarine Squadron in the 1st Squadron, based in Brest France.[2][3] Her sister ships Ajax, Archimède, and Persée made up the rest of the division.[2][3]

On 20 September 1939, Poncelet and Persée departed Brest to patrol in the Atlantic Ocean to the north and south of the Azores, where seven German merchant ships — which the Allies suspected of serving as supply ships for German U-boats — had taken refuge at the start of the war.[2][4] On 23[5] or 28[2] September 1939 (according to different sources), Poncelet became the only French submarine whose crew boarded an enemy merchant ship during World War II when she captured the German cargo ship Chemnitz. Chemnitz — making a voyage from Durban, South Africa, to Hamburg, Germany, with a cargo of 2,500 tonnes (2,460 long tons; 2,760 short tons) of lead ore, 2,000 tonnes (1,970 long tons; 2,200 short tons) of lead, 1,000 tonnes (980 long tons; 1,100 short tons) of wheat, 850 tonnes (840 long tons; 940 short tons) of flour, and 500 tonnes (490 long tons; 550 short tons) of barley — had slipped out of Las Palmas on Gran Canaria in the Canary Islands in an attempt to reach Germany, but Poncelet captured her 70 nautical miles (130 km; 81 mi) south of Faial Island in the Azores and took her as a prize, sending her to Casablanca in French Morocco under the control of a prize crew.[2][5] Poncelet then proceeded to Cherbourg, France, along with Persée for a refit.[2][6]

German ground forces advanced into France on 10 May 1940, beginning the Battle of France. Poncelet departed Cherbourg, then called at Brest. Italy declared war on France on 10 June 1940 and joined the invasion. As the Germans approached Brest, Poncelet evacuated the base, getting underway at 18:30 on 18 June 1940 with the submarine tender Jules Verne and 13 other submarines,[2] including her sister ships Ajax, Casabianca, Persée, and Sfax. They arrived at Casablanca on 23 June 1940.[2][7] On 25 June 1940, the Battle of France ended in France's defeat and an armistice with Germany and Italy that went into effect that day.

After France's surrender, Poncelet served in the naval forces of Vichy France. After the British Royal Navy attacked the French Navy squadron at Mers El Kébir, French Morocco, on 3 July 1940, Poncelet was assigned along with Casabianca and Sfax to defensive patrols off French Morocco, the three submarines combining to maintain a continuous offshore presence from 6 to 18 July 1940, when the submarines Amphitrite, Calypso, and Méduse relieved them.[2][8]

On 8 August 1940, the French Navy put a reorganization into effect which placed Poncelet and Persée in the 6th Submarine Division and transferred them to Dakar in Senegal.[2] On 2 September 1940, Poncelet got underway from Dakar with the aviso Bougainville and the banana boat Cap des Palmes, which was loaded with troops and supplies. Poncelet escorted Cap de Palmes as she approached Mayumba on the coast of Gabon — then a territory of French Equatorial Africa — to land the troops, but the landing was cancelled when the French discovered British forces at Mayumba.[2] Poncelet then proceeded to Port-Gentil in Gabon.[2][9] As of 26 October 1940, she remained at Port-Gentil.[2]

On 7 November 1940, Free French forces began amphibious landings to capture Gabon from Vichy France,[10] resulting in the Battle of Gabon. At the time, Poncelet, which was at Port-Gentil, and Bougainville, which was at Libreville, were the only Vichy French vessels available for the defense of Gabon.[11] British forces provided cover for the landings, and at 06:30 Alpha Time on 7 November the Royal Navy heavy cruiser HMS Devonshire[10] — flagship of the British task force commander, Admiral John Cunningham[12] — launched a Supermarine Walrus biplane flying boat to search for Poncelet.[10] It returned at 07:45 Alpha Time and reported that Poncelet was anchored off Port-Gentil, 8 nautical miles (15 km; 9.2 mi) and bearing 138 degrees from Cape Lopez.[10]

Poncelet had put about a quarter[2] or a third[10] (according to different sources) of her crew ashore to reinforce the Vichy French garrison at Port-Gentil,[10] but she received orders to attack the transports carrying the Free French invasion force[11] off Libreville[2] with the crew she had on board, and she set out toward the Baie des Baleiniers.[2] She sighted the masts of the Royal Navy sloop-of-war HMS Milford,[2] which was on antisubmarine patrol to the north and northeast of Cape Lopez, and at 15:52 Alpha Time, Milford reported that Poncelet had gotten underway.[10] At 16:15, Milford reported Poncelet zigzagging on the surface on a course of 60 degrees, while Milford herself was making 16 knots (30 km/h; 18 mph) on a course of 60 degrees.[10] At 16:19, Milford reported her own position as 00°20′S 008°50′E and that Poncelet was 7 nautical miles (13 km; 8.1 mi) distant, bearing 30 degrees and still on a course of 60 degrees.[10]

HMS Milford in June 1944.

Milford was too slow to intercept Poncelet as long as Poncelet remained on the surface and undamaged, so Cunningham ordered Devonshire to launch a Walrus to attack Poncelet in the hope of either damaging her or forcing her to dive, which in either case would slow her and give Milford a chance to overtake her.[10][12] Devonshire launched the Walrus at 16:50 Alpha Time.[10] At 17:00 Alpha Time, Milford reported herself at 00°11′S 008°57′E and that Poncelet was 6.5 nautical miles (12.0 km; 7.5 mi) distant, making 16 knots (30 km/h; 18 mph) and steering a course of 39 degrees.[10] The Walrus straddled Poncelet with two 100-pound (45 kg) depth charges, damaging her and forcing her to submerge.[10][12]

At 17:20 Alpha Time, Milford reported that Poncelet had altered course to the west and submerged and that she was engaging Poncelet.[10] Poncelet fired a torpedo at Milford which passed under Milford without exploding.[10][13] Poncelet attempted to fire a second torpedo, but it got stuck in its tube, gave off toxic smoke into the interior of the submarine, and created a leak.[10][13] Milford depth-charged Poncelet, damaging her and forcing her to the surface, then opened gunfire on her.[2] She submerged again, but was too badly damaged to withstand the dive, and her crew faced the danger of asphyxiation from the smoke emitted by the torpedo, so Poncelet′s commanding officer, Capitaine de corvette (Corvette Captain) Bertrand de Saussine du Pont de Gault, ordered the submarine to surface and her crew to abandon ship.[2][13] Soon after engaging Poncelet, Milford reported that Poncelet had surfaced at 00°04′S 008°56′E.[10]

The British light cruiser HMS Delhi received orders at 18:01 Alpha Time to close with Poncelet and put a prize crew aboard her.[10] At 18:05, Milford signaled that Poncelet′s engines had broken down and that she had surrendered.[10] Once certain that his crew was safe, de Saussine went back aboard Poncelet and opened her seacocks, scuttling her at 00°20′S 008°50′E to prevent her from falling into enemy hands.[10][13] He decided to remain aboard as she sank and went down with his ship, the only member of Poncelet′s crew lost in her sinking.[2][11][13][14][15] At 18:20, Milford reported that Poncelet had been scuttled and that she was picking up survivors.[10] Although Delhi received orders to assist in the rescue, Milford brought aboard all 54 survivors — three officers and 51 enlisted men.[10]

• Clayton, Anthony (2014). Three Republics, One Navy: A Naval History of France 1870–1999. Solihull, England: Helion & Company Limited. ISBN 978-1-911096-74-0.
• Fontenoy, Paul E. (2007). Submarines: An Illustrated History of Their Impact (Weapons and Warfare). Santa Barbara, California. ISBN 978-1-85367-623-9.{{cite book}}: CS1 maint: location missing publisher (link)
• Gardiner, Robert; Chesneau, Roger (1980). Conway's All the World's Fighting Ships 1922–1946. London: Conway Maritime Press. ISBN 0-85177-146-7.
• Huan, Claude (2004). Les Sous-marins français 1918–1945 (in French). Rennes: Marines Éditions. ISBN 9782915379075.
• Jennings, Eric T. (2015). French Africa in World War II. Cambridge University Press. ISBN 978-1107048485.
• Montety, Étienne de (2001). Honoré d'Estienne d'Orves: Un héros français (in French). Paris: Perrin. ISBN 978-2-262-01576-3.
• Ntoma Mengome, Barthélémy (2013). La bataille de Libreville: De Gaulle contre Pétain : 50 morts (in French). Paris: L'Harmattan. p. 88. ISBN 978-2-343-01045-8..
• Picard, Claude (2006). Les Sous-marins de 1 500 tonnes (in French). Rennes: Marines Éditions. ISBN 2-915379-55-6.