In the official account, Kormoran prolonged the identification exchange by signalling slowly and awkwardly. The disguised raider also transmitted a false merchant distress message about a suspicious ship. Sydney continued trying to verify the ship's identity and eventually requested a secret identification response that Kormoran could not supply. The failure of that challenge brought the deception to an end and preceded the opening gunfire.
Notable Point · 1:36:40-1:40:14
Kormoran's slow signals and the secret challenge
Slow signalling and a false distress message prolonged Kormoran's disguise until Sydney demanded a secret identification response.