Designed by the naval architectEmile Bertin, the Gueydon-class ships were intended to fill the commerce-raiding strategy of the Jeune École. They measured 137.97 meters (452 ft 8 in) long overall with a beam of 19.38 meters (63 ft 7 in) and had a draught of 7.67 meters (25 ft 2 in). Dupetit-Thouarsdisplaced 9,367 metric tons (9,219 long tons). The ship had a crew of 566 officers and enlisted men.[2]
The Harveyarmor belt of the Gueydon-class cruisers covered most of the ships' hull. The lower strake of armor was generally 150 millimetres (5.9 in) thick, although it reduced to 91 millimetres (3.6 in) forward, 81 millimetres (3.2 in) aft. The curved lower protective deck ranged in thickness from 51 to 56 millimetres (2.0 to 2.2 in). The gun turrets were protected by 160–176-millimetre (6.3–6.9 in) armor and had roofs 23 millimetres (0.9 in) thick.[2][3]
In 1918, she was part of the Atlantic Naval Division, under Commander Paqué, and tasked with escort duty. On 7 August 1918, escorting a 24-ship convoy inbound from New York, she was torpedoed by the submarine U-62, off Brest. At nightfall, at 20:51, a torpedo hit the port side underneath the forward bridge, followed ten seconds after by another under the aft bridge. The explosions killed three men, and neither the submarine nor her periscope were spotted, although a Lieutenant detected the first torpedo shortly before it hit.[4]
Assessment of the ship soon revealed extensive damage, but as the list was moderate, the officers deemed that although the ship was lost, she would not sink rapidly. They moved the ship off the route of the convoy, radioed a distress call, and stopped the engines to allow the crew to evacuate. The list then started to increase while the crew abandoned ship. Fifty minutes after the torpedo hit, Dupetit-Thouars rolled over and sank, killing ten sailors still aboard trying to launch the last raft. Following the sinking, U-62 surfaced to inquire as to the name and tonnage of the cruiser, and collect a ribbon from a sailor's hat.[4]
Dupetit-Thouars was mentioned in dispatches at the Army level on 25 October 1919, the mention stating
the armoured cruiser Dupetit-Thouars: during an escort mission, was torpedoed and sunk on 7 August 1918 by an enemy submarine. The whole personnel demonstrated, in these circumstances, the greatest calm and the high dedication.[4]
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Friedman, Norman (2011). Naval Weapons of World War One: Guns, Torpedoes, Mines and ASW Weapons of All Nations; An Illustrated Directory. Barnsley, UK: Seaforth Publishing. ISBN978-1-84832-100-7.
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Roberts, Stephen S. (2021). French Warships in the Age of Steam 1859–1914: Design, Construction, Careers and Fates. Barnsley, UK: Seaforth Publishing. ISBN978-1-5267-4533-0.
Silverstone, Paul H. (1984). Directory of the World's Capital Ships. New York: Hippocrene Books. ISBN0-88254-979-0.