He was a member of the political organization Sudara (Sumber Darah Rakyat). An organisation formed by
Andi Mappanyukki and
Sam Ratulangi who was at the time advisor 2nd South Fleet of the Imperial Japanese Navy military government for East Indonesia, alongside Arung Tomarilaleng Bone, Opu Tomarilaleng Palopo, Arung Enrekang. Bau Massepe would lead the branch in Parepare. In September 1945, Bau Massepe used his authority as Datu Suppa and Bunken Kanrikan, changed Sudara to Badan Penunjang Republik Indonesia ( Support Agency for the Republic of Indonesia) with him being the chairman. This organization is formed to support and defend the proclamation of independence. In
Parepare with the support of
Sam Ratulangi, the organization Komite Nasional Indonesia (KNI) transformed to PKRS, Pusat Keamanan Rakyat Sementara ( Temporary Center for People's Safety) under Massepe. This organization stockpiled weapons, bought and stole Japanese weapons, organize plans, and sabotage Dutch roads. Other militia organisation he would form include Pemuda/Pandu Nasional Indonesia (PNI) and Lasykar BP. Ganggawa. Anti-Dutch riots erupted especially after
Proclamation of Indonesian Independence. Situations in
Makassar got more heated on 2 October 1945, when a Dutch forces shot people with red and white badge, retaliatory attacks happened for three days afterward. Orders were restored after
gentlement agreement between Brig. Gen.
Ivan Dougherty and Gov.
Sam Ratulangi. However situation in Makassar inspired similar movements in
Parepare and Suppa, Bau Massepe alongside BPRI and Pemuda/Pandu Nasional Indonesia (PNI) hold daily meetings to counter allied forces. On 15 October 1945, a meeting was held between all kings of South Sulawesi in Jongaya led by King of Bone,
Andi Mappanyukki, that resulted in a pledge to support of republican government under Gov.
Sam Ratulangi and reject Dutch authority. This pledge was then delivered in person by
Andi Mappanyukki to allied leadership of Brig. Gen.
Ivan Dougherty with NICA representative Major Wagner present. On 20 October Bau Massepe forces was involved in a battle with KNIL in Padang Loangnge'. On 22 October 1945, another meeting between kings in Parepare afdeeling held by Bau Massepe, resulted in similar pledge. On 25 October, further contacts were made in Kariango or Pajojoreng. On 21 November 1945 Brig.
Chilton issued a notice to shoot dead on the spot for any that have guns, explosives, keris, badik and spear, that infuriated pemuda and civilians resulting in worsening situation. Bau Massepe sent delegations to
Yogyakarta, this delegation included Muhammad Saleh Lahade, Andi Mattalatta, Capt. La Nakka, Muhammad Amin and Lanca. On 28 January 1946, these delegations arrived in Yogyakarta and received by
Sukarno, furthermore Massepe also sent pemuda to receive military training and weapons from Java, notable figures include M. Daeng Malewa, Andi Oddang, Andi Sapada Mappangile, Arsyad B., Andi Sapada Wette, Abdullah, and Musa Gani. In January 1946 a battle happened in Bonrongnge', Bau Massepe tried to attack NICA post on 3 February 1946, but failed, another attack happened in Bacukiki, and March 1946 in Polejiwa and Tiroang Pinrang. La Nakka and Muhammad Amin returned to Bau Massepe in April 1946 with provision that Andi Mappanyukki as Colonel, and Sultan Daeng Raja, Andi Pangerang Pettarani, Bau Massepe as Lieutenant Colonel. Further communication from Yogyakarta was received asking Dutch troop numbers and possible landing sites, although Dutch Military Police arrived to BPRI central office to confiscate the letters, Bau Massepe managed to escape with the help of A.J. Binol. According to the letters around 6000 soldiers have finished military training will arrive in waves. In May 1946, Dutch troops would be intercepted in Menuang, Alitta, and further contact would occur in Manggarongkong and Lakessi. In July 1946, a general attack on NICA position in Rappang would be launched, while a battle in Carawali would occur on 26 August 1946. La Nakka was again to be sent from Suppa to Java in August 1946, meanwhile Bau Massepe would stay to coordinate the pemuda in Sulawesi. In 1946, all year-round multiple attacks on KNIL positions were launched consecutively in Libukang/Kabaena, Uli-Uli Tanae', Langsangenge', Bulu Manggarongkonge', Cappa Galung, Lacori/Alitta, Teppoe'/Alitta, Wae' Sibokorongnge', Bungi Kelapa Dua Butt/Suppa, Toe'/Alitta, Pucue', Inru Kinrue', Labuangnge', Allemeangnge', Lajojoreng, Batu Terpedo, Leppangeng, Bonging-Ponging, Labalakang, Mattiro Sompe, Bau Massepe would intercept the Dutch troops in Lamajakka/Suppa in which the Dutch suffered heavy losses, Teppoe'/Alita, in Lasekko/Suppa Dutch troop would attack civilians in Berpuru, Karabello, Allakarajae', Bau Massepe troops would beat Dutch forces in Garessi/Suppa in which Dutch Major F. La Roy would be killed. He managed to push back Dutch forces in Teppoe Kanango and stole some weapons. Eventually Bau Massepe with Andi Sodji were captured on 17 October 1946. He was brought to
Makassar, and imprisoned for 160 days. On 20 January 1947, in Paccekke Conference led by Major Andi Mattalatta, TRI Hassanuddin Division I would be formalised, and Bau Massepe would be the commander
in absentia with the rank Major General. ==Imprisonment and death==