In August 1942, Matthes was ordered to Lublin reservation, where he was in short time drafted into the SS with the rank of Scharführer (Sergeant), dispatched to Operation Reinhard, and sent to Treblinka extermination camp. There he was appointed chief officer commanding Camp II (the extermination area) and the gas chambers.[2] Matthes was remembered by fellow Treblinka SS officer Franz Suchomel in the following way: