On 23 September 1940, she arrived at Dakar with "Persée" and "Poncelet". On the 23rd, she sighted the British force preparing to attack Dakar. She turned to attack it along with "Persée", who was quickly sunk by British depth charges. "Ajax" itself was forced to crash-dive and was then depth charged, but sustained only minor damage. The next day, she attempted to torpedo the battleships and but was detected on sonar and critically damaged by depth charges from the destroyer . She was forced to surface and scuttled by its crew, most of which was then rescued by lifeboats from "Fortune".