Hettier de Boislambert was now promoted to the rank of squadron leader ahead of the attempt on 23 September 1940 to capture the strategically important port city of Dakar from the pro-German Vichy French administration of what was then known as French West Africa (modern-day Senegal). The attempt failed, however. Hettier de Boislambert was given charge of the land-based support operation for the Franco-British landing which in the end had to be aborted. After five days at liberty during which he was able to piece back together many of the resistance elements which had been disrupted during the operation, he was himself one of the two resistance leaders captured in the jungle by Pro-Vichy forces on 30 September 1940. There followed long weeks of interrogation in prisons at Dakar and, later, Bamako during which he faced, among others, the Vichy-appointed colonial governor general , but sources insist that these sessions left his interlocutors and their Vichy bosses none the wiser about the resistance activities in which he had been engaged.