The war of the Triple Alliance begins. Brazil, Uruguay, and Argentina defeat Paragua The War of the Triple Alliance (1864–1870) was a conflict in which Brazil, Argentina, and Uruguay (the Triple Alliance) defeated Paraguay. It began when Paraguay’s leader, Francisco Solano López, declared war on Brazil and later Argentina, aiming to protect Paraguay’s interests and expand its influence. The war resulted in massive destruction for Paraguay, significant loss of life, and its eventual defeat, leaving the country devastated economically and demographically.