"Where are the explosives? I want an answer now, otherwise I will personally rearrange this officer's splints."Hauptsturmführer Sessler was an SS officer stationed on Navarone during World War II. When he received word that the British commandos led by Keith Mallory had been captured, the island's commandant sent Sessler to interrogate them. Sessler was a brutal and sadistic man, and despite the objections of Oberleutnant Muesel he attempted to torture the injured Major Roy Franklin.
Before he could, Andrea Stavros staged a breakout. Sessler was grabbed in a headlock by Stavros and subdued. He, Muesel and their guards were tied up, and their uniforms appropriated by the commandos; in particular, Sessler's uniform was taken by Corporal Miller. Later, Sessler did torture the captured Franklin in an effort to learn about Mallory's plans, but his efforts failed to break the Englishman. The annoyed commandant called Sessler off and ordered Franklin be given a truth drug instead. A disappointed Sessler left with the commandant.
- Sessler's uniform lacks any shoulder decorations. He is also missing the eagle insignia on his upper left arm.
- Muesel refers to Sessler incorrectly as "Hauptmann."