From Halopedia, the Halo wiki
Oscar Bauer was the last leader of the Frieden movement. He was the nephew of Nadja Mielke, who had led the Frieden until she was assassinated in December of 2163. The last of the Frieden forces fought savagely against the United Nations Space Command under Bauer during large-scale invasions on Europa, Io, Ganymede, and Callisto. However, by mid-2169, little remained of the movement.