López, believing that he could deal a fatal blow to the Allies, launched a major offensive with 25,000 men against 35,000 Allied soldiers at the Battle of Tuyutí on 24 May 1866, one of the bloodiest battles in Latin-American history. Despite being very close to victory at Tuyuti, López's plan was shattered by the Allied army's fierce resistance and the decisive action of the Brazilian artillery. Both sides sustained heavy losses: more than 12,000 casualties for Paraguay versus 6,000 for the Allies.