Rubuta ci gaba don wannan sakin layi - López, yana gaskanta cewa zai iya ba da mummunan rauni ga Allies, ya kaddamar da wani babban hari tare da mutane 25,000 da sojoji 35,000 a yakin Tuyutí
a ranar 24 ga Mayu, 1866, daya daga cikin fadace-fadacen da suka fi zubar da jini a tarihin Latin Amurka. Duk da kasancewa kusa da nasara a Tuyuti, shirin López ya lalace saboda tsananin juriya na sojojin Allied da kuma yanke shawara na bindigogi na Brazil. Dukkanin bangarorin biyu sun sha wahala sosai: sama da mutane 12,000 na Paraguay da 6,000 na Allies.