Paraguay’s initial thrusts into Brazil and Argentina were soon blunted, and Lopez was forced on the defensive for the balance of the conflict. On, in response to Lopez’s attacks, Argentina, Brazil, and Uruguay formed an alliance and declared war on Paraguay. Not content with Brazil as an enemy, he provoked Argentina by crossing Missiones Province to attack Brazil from the west.
Lopez was convinced that Brazilian dominance of Uruguay would upset the balance of power in the region, and he reacted by blocking the Paraguay River and invading Brazil’s Matto Grosso Province. The war began in November 1864, when Brazil meddled in Uruguay’s internal affairs, an action that drew an immediate response from Paraguay’s bellicose dictator, Marshal President Francisco Solano Lopez. South America’s longest and most violent war.
