Complex sentence: Soeprijadi, a PETA soldier who had led an uprising against Japanese forces in Blitar in February 1945, was thought dead, and while Soeljohadikosomo's position remained unfilled, the guerrilla leader Moestopo declared himself Minister of Defence.
Split into simpler sentences: Soeprijadi, a PETA soldier who had led an uprising against Japanese forces in Blitar in February 1945, was thought dead. While Soeljohadikosomo's position remained unfilled, the guerrilla leader Moestopo declared himself Minister of Defence.