Manuel Bulnes was elected a deputy for Mulchén in 1879. At the beginning of the War of the Pacific, he organized a cavalry squadron that they named "Escuadrón de Carabineros de Yungay", but the transport "Rimac" where they were traveling to the theater of operations was captured en route by the Peruvian Navy and they were interned as prisoners of war in the city of Tarma. Himself and his squadron were later freed via prisoner exchange, and they fought at the battles of Tacna, Chorrillos and Miraflores.