While Mümin was director of the intelligence services, his uncle Hacı Hasan Paşa worked with the Greek administration.

Mümin continued his duties in Izmir with the aid of his uncle and presented himself as a Turkish officer working on behalf of the Greek administration.

He was given the nicknames Gavûr Kirye and Hain Mümin by the Turkish population of Izmir, who did not know the truth of his activities.

Mümin Paşa's activities were discovered by the Greek force and he was arrested before the Great Offensive and taken to the Palamadi prison.

After the Armistice of Mudanya he was sent to Palya İstratona prison, and eventually he went moved to the Lusiya Esir Camp.