Utilizing both primary and secondary literature, this study attempts to illustrate that the origins of one of Latin America’s most significant wars, the Paraguayan War (1864-70), are understandable only when viewed within the context of the historical development of the Rio de la Plata as a region. Adopting the framework provided by Robert N. Burr in his pioneering work on the South American continental balance of power system. “By Reason or Force: Chile and the Balancing of Power in South America, 1830-1905” (Berkely, 1965), this thesis examines one particular outgrowth of the historical process in the Rio de Plata: The development of a regional balance of power in the area. It also illustrates that such systems of international power politics are not necessarily promotive of stability and equanimity in the relations between nations: that balance of power systems are not static but constantly changing, and that such changes are conducive to friction, intrigue, and war.