Rubuta ci gaba don wannan sakin layi - A ranar 2 ga Mayu, 1866, ya halarci Yaƙin Estero Bellaco, wani yanki na ƙasa wanda ruwan Kogin Paraná ya haɗu da ruwan Kogin Paraguay, inda abokan gaba suka fara jinkirta sojojin haɗin gwiwa, suna neman kyakkyawan matsayi don yin yaƙi. A ranar 24 ga Mayu, 1866, ya halarci Yaƙin Tuyutí
, babban yaƙi a Kudancin Amurka, inda ya taka muhimmiyar rawa wajen ba da umarnin cibiyar sojan rundunar sojan Brazil a kan harin Paraguay. Ya rubuta a kan Dokar Ranar # 56: "Girma ita ce kyauta mafi daraja na jarumi". A ranar 15 ga Yuli, 1866, har yanzu a Tuyuti, abokan haɗin gwiwa suna jiran isowar sojojin Janar Count of Porto Alegre, yayin da abokan gaba ke bulala yau da kullun. Ya ji rauni sosai a yaƙin kuma bai gamsu da tsawon lokacin da sojojin suka tsaya ba, Osório ya ba da umarnin sojojin Brazil ga Janar Polidoro da Fonseca Quintanilha Jordão.