Japan officially surrendered on 15 August 1945, and Indonesia declared its independence two days later. On the morning of 23 August 1945, Adnan Kapau Gani held a meeting to discuss the post-independence government of South Sumatra. Mohamad Isa, who attended the meeting, held office as the head of the oil and mining affairs in South Sumatra. In his capacity as the head of the oil and mining affairs, Mohamad Isa was appointed as the CEO of PERMIRI ("Perusahaan Minyak Republik Indonesia", Oil Company of the Republic of Indonesia). PERMIRI was the first oil company in Indonesia that was managed by Indonesians. PERMIRI was established by Adnan Kapau Gani and operated leftover oil refineries in South Sumatra, which was previously owned by NIAM ("Nederlansch Indie Aardolie Maatschappij") and BPM ("Bataafsche Petroleum Maatschappij"), both of which were Dutch East Indies era oil companies. Mohamad Isa's main task as the CEO was to repair the oil refineries in Plaju (previously owned by BPM) and Gerong River (previously owned by NIAM). Both refineries suffered heavy damages due to the bombing campaign conducted by the Allies in 1944.