French submarine Danaé

On 11 July 1932, Danaé participated briefly in the investigation of the loss of the submarine Prométhée,[1] which had sunk suddenly in the English Channel during her sea trials on 7 July 1932 with the loss of 62 lives.[3]

In November 1934 Danaé and the submarines Amazone, Méduse, and La Psyché visited Leith, Scotland.[4]

When World War II began on 1 September 1939 with the German invasion of Poland, Danaé was part of the 14th Submarine Division — a part of the 2nd Submarine Squadron in the 6th Squadron — along with her sister ships Ariane and Eurydice and the submarine Diane, based at Oran in Algeria.[1] France entered the war on the side of the Allies on 3 September 1939. 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. The Battle of France ended in France's defeat and an armistice with Germany and Italy on 22 June 1940. When the armistice went into effect on 25 June 1940, Danaé still was based at Oran.[1]

After France′s surrender, Danaé served in the naval forces of Vichy France. On 3 July 1940, the British began Operation Catapult, which sought to seize or neutralize the ships of the French Navy to prevent their use by the Germans, and Danaé was in port at the French naval base at Mers El Kébir at Oran that day when a British naval squadron arrived off the base and demanded that the French Navy either turn over the ships based there to British custody or disable them. The French put their submarines at Oran on alert,[1] and at 15:00 Danaé and Ariane were ready for sea.[1] They anchored in the outer harbor at 15:30 with Diane and Eurydice,[1] and at 17:54 the four submarines received orders to put to sea.[1]

When the British warships opened fire on the French ships in the harbor at 17:57,[1] beginning their attack on Mers-el-Kébir, Danaé was 4 nautical miles (7.4 km; 4.6 mi) west of Ariane, which was 4 nautical miles (7.4 km; 4.6 mi) west of Diane, which in turn was 3.5 nautical miles (6.5 km; 4.0 mi) west of Pointe de l’Aiguille (35°52′31″N 000°29′04″W) in Oran Province.[1] None of the four submarines was able to close with the British ships during the battle.[1] After dark, a British aircraft sighted Danaé and Eurydice and dropped illuminated marker buoys to guide a British destroyer to them.[1] The destroyer depth-charged the two submarines, but they escaped damage.[1] During the night of 3–4 July 1940, the four submarines patrolled on the surface off Oran in a north-south patrol line.[1] They remained on patrol off Oran until 20:00 on 4 July 1940 before returning to Oran.[1]

In October 1940, Danaé was placed under guard at Oran in an unarmed and unfueled status in accordance with the terms of the 22 June 1940 armistice.[1]

Danaé still was in this status when Allied forces invaded French North Africa in Operation Torch on 8 November 1942.[1] She was scuttled at Oran on 9 November 1942 to prevent her capture by Allied forces.[1]

• Moulin, Jean (2006). Les sous-marins français en images (in French). Rennes: Marines Éditions. pp. 14–15. ISBN 2-915379-40-8..
• Donald A. Bertke; Don Kindell; Gordon Smith; Susan A. Bertke (2011). World War II Sea War: France Falls, Britain Stands Alone: Day-to-Day Naval Actions from April 1940 through September 1940. Vol. 2. Lulu.com. p. 192. ISBN 978-1-937470-00-5..