Because of the Japanese attack, he joined the army school (PETA). Then, he was promoted to be a Daidanco (Batalyon commandant) in Kroya. After Indonesia got the freedom, formed a BKR (Badan Keamanan Rakyat), that the members are a former PETA, KNIL,Heiho and other forces. After BKR was changed to TKR (Tentara Keamanan Rakyat) October 5, 1945. Soedirman was promoted into “Chief of the 5th division of Banyumas”. That day was called the”Angkatan Bersenjata Republik Indonesia” (ABRI). At November 12, 1945, he was promoted to the 5 big General of Indonesia. The last war he been through is the Geriliya War.