Paraguay is a free print-and-play wargame about the 1864 war involving Brazil, Uruguay, Paraguay and Argentina. It’s designed for 2 – 4 players.
Natholeon’s Empire offers a set of free wargames rules for the War of the Triple Alliance.
The War of the Triple Alliance, also known as the Paraguayan War, was fought between 1864 and 1970 between Paraguay and the Triple Alliance of Argentina, Brazil, and Uruguay. Percentage-wise, it was one of the most devastating wars in history, with Paraguay losing 70% of its adult male population.