An experienced naval officer, he specialized in submarine warfare shortly before World War II.

After the armistice of 22 June 1940, he decided to join Free France and subsequently operated in the Mediterranean Sea, where he disappeared with the entire crew of his submarine.

[7][9][11] He earned lasting fame[7][11] with a message he transmitted en route, which stated, "Betrayal [also translated as "Treason"] all along the line, we are headed for an English port,"[7][10] expanded by one source to read "Betrayal all along the line, we are headed for an English port to continue the fight against the Germans!

[9] Italian divers discovered Narval′s wreck — her bow split open, apparently by a mine[9] — off the Kerkennah Islands in the Gulf of Gabès off the coast of Tunisia in October 1957,[4][9] leading to the conclusion that she apparently struck a French mine in a defensive minefield, probably on 15 December 1940.

[5][6][13][14][15] In his 2003 book The Fighting Tenth: The 10th Submarine Flotilla and the Siege of Malta, John Wingate relates a different account of the loss of Narval in which she departed for her third patrol on 29 December 1940 and was due to return from it on 11 January 1941, but was rammed and sunk with the loss of all hands by the Italian torpedo boat Clio — which recovered lifebelts with Narval′s name on them, but no survivors — and was declared missing by British authorities at Malta on 14 January 1941.

[16] In his 2011 book The SURCOUF Conspiracy: A Penetrating Analysis of the Worst Submarine Disaster in History, John Grigore Jr. specifies that Clio sank Narval off Derna on 7 January 1941.

In September 1941, the Vichy French Admiralty fabricated a rumor that Drogou, deciding that he had misunderstood his duty to France and that the Free French had misled him, had left Malta in an attempt to reach metropolitan France, and that the Royal Navy had assassinated Drogou by sending two warships after Narval, which had sunk her with all hands.