Indonesia proclaimed its independence on 17 August 1945, and Resobowo worked to spread this news. Together with M. Balfas, he designed posters related to Indonesian independence which he spread through the "kampung" of Jakarta (renamed during the occupation). He was also a member of the Menteng 31 group. However, when the returning Dutch colonial forces forced the republican government out of Jakarta in 1946, Resobowo left the city. He spent the remainder of the Indonesian National Revolution (1945–1949) in cities such as Yogyakarta, Madiun (where he sketched Lake Sarangan), and Sukabumi. When he was living in Madiun he worked with Sudjojono, Sudibio, and Trisno Sumardjo to establish the Young Indonesian Artists (, or SIM); he remained active with this group even after moving to Surakarta and Yogyakarta.