In the Peruvian-Colombian war of 1828/29 Braun fought on the side of Simón Bolívar, Antonio José de Sucre and Juan José Flores. After a failed diplomatic mission as official representative of the victors Braun had to flee ending up in Valparaíso, Chile (1829). A few months later Braun was able to travel to Arequipa, Peru, where finally met his wife Justa Germana de Rivero y Abrill, which he had married through written authority in 1828.