Nearly 300 years ago, two great alliances collided on the Great Plains in a battle that changed the course of American history. But until now, no physical evidence of the storied conflict had ever been found. In the summer of 1720, where the Platte River meets the Loup in eastern Nebraska, Spanish soldiers, New Mexican settlers and their Pueblo and Apache allies clashed with warriors from the Pawnee and Oto nations of the Plains. In a daybreak raid, the Pawnee and the Oto — possibly with the support of French traders — routed the Spanish, killing their commander, Don Pedro...