First Brazilian-Argentinian War (Qu'il Tous)

Background
The war's background goes back to the events succeeding the War of South American Independence, where Brazil had become a very influential power in South America, but had a clear enemy, Argentina. The two had continuously been fighting against each other politically over territories such as Paraguay and Uruguay, but Brazil had remained clearly on top through a larger military and population. But Argentina had managed to excel in one category that Brazil often ignored, building up alliances with other nations. The Argentines had built up a modest alliance with Chile and Paraguay. And each of them being republic's made this political stand-off a philosophical challenge between republicanism and imperialism.

The other main cause of the war was continental masterism, a political belief that every continent should have one premier power to run it politically. France and the United States had already been proven as the masters of their respective continent's, but the master of Asia, Africa, and South America was still unclear. The Brazilians had also established themselves in an international alliance lead by France, called the Continental Alliance, consisting of France, the United States, Brazil, the Confederation of the Rhine, Iberia, Denmark-Norway, Ireland, Italy, and Poland. Argentina, meanwhile, was working out an alliance with the resurgant Great Britain, along with Russia, Austria, Prussia, and Sicily.

But the final blow in tensions came when the provincial government of the Brazilian province of Uruguay sent a message to the Argentine Republic, asking for their help in winning independence from Brazil. The Argentines called up their local alliance and declared war on Brazil on November 12, 1866, and Brazil prepared its army for war.