The Paraguayan War (1864–70) was the deadliest and most extensive interstate war ever fought in Latin America. The conflict involving Paraguay, Uruguay, Argentina, and Brazil killed hundreds of thousands of people and had dire consequences for the Paraguayan dictator Francisco Solano López and his nation. Though the Paraguayan War stirs the same emotions in South Americans as does the Civil War in the United States, there have been few significant investigations of the war available in English.

In this first of two volumes, Thomas L. Whigham provides an engrossing and comprehensive account of the war's origins and early campaigns, and he guides the reader through the complexities of South American nationalism, military development, and political intrigue. Whigham portrays the conflict as bloody and inexcusable, though it paved the way for more modern societies in the continent. The Paraguayan War fills an important gap in our understanding of Latin American history.