Fluvial Wars (Spanish: Guerras Fluviales; Portuguese: Guerras Fluviais), or Big Stream Wars, or, more recently, Continental Wars, is the name given by historians to a series of major continental wars that took place in 19th century South America. The name is due to these wars being fought around some of the continent's big rivers - namely River Plate, San Francisco River, and Paraguay River. All wars happened in the mid-century between 1825 and 1875, and were decisive to shape the continent's political frontiers.
The main Fluvial Wars were:
River Plate War (Spanish: Guerra del Río de La Plata);
Uruguay River War (Spanish: Guerra del Uruguay; Portuguese: Guerra do Uruguai)
Upper Parana River War (Portuguese: Guerra do Paraná)
San Francisco River War (Portuguese: Guerra do São Francisco or Guerra do Sertão);
War of Paraguay (Spanish: Guerra de Paraguay [In Paraguay: La Guerra Grande]; Portuguese: Guerra do Paraguai)
The term "Fluvial Wars" was coined in 1876 by a Bahian historian to describe a series of wars who were supposedly related to each other. The relation among the wars, in his interpretation, was not mere coincidence: the continent's major rivers, along with mountain chains, were considered the "natural international borders", but every country leader tried to push forward their dominions to the next river or the next chain.
The fact that South America witnessed so many major wars in the mid-1800s, all of them fought around strategical points of the continent, demonstrates that the process of independence and consolidation of national borders was a very harsh one.
River Plate War - fought in the 1820s, it was a result of the process of fragmentation of Viceroyalty of Río de La Plata (Spanish: Virreinato del Río de La Plata) and the formation of many Republics on its former territory.
Uruguay River War - A consequence of River Plate War, it was an attempt of United Provinces of Rio de La Plata (now Argentina) to take back the lands west to Uruguay River, who had been granted to Portugal in 1801.
San Francisco War - Land disputations among many newly created countries around San Francisco River led to a major conflict that involved several countries over the vast region of San Francisco Outback (Portuguese: Sertão do São Francisco or Comarca do São Francisco). Eventually, the region was taken by Maranhão Republic.
Tocantins River War - Soon after the end of San Francisco War, a conflict involving Maranhão and Pará Republic led to another war on the Tocantins region, which ended by being split along the river's line.
Paraguay War - The last of the region's major conflicts, it involved eight countries and is considered to be the greatest war on American continent ever.