By the third decade of the 19th century the growing American nation had expanded so far into the Florida peninsula that in 1832 a group of Semile tribal chiefs accepted the terms of a treaty which provided for the removal of their tribes to the West. Wiley Thompson was appointed to supervise the migration. However, a great number of the Semiles were deeply attached to their homeland and fiercely opposed exchanging their Florida land for that promised in the West. On December 28, 1835, warriors led by Osceola massacred Thompson and a number of American citizens, thereby beginning the Second Semile War. It continued for almost seven years and would become the most expensive of all the American Indian wars, in both monetary and human terms. After the war John T. Sprague, who had participated in the war during its last years, published The Origin, Progress, and Conclusion of the Florida War , for 120 years the only account of this episode in US history. Drawing on data, resources and insights unavailable to Sprague, Mahon sets out to bring a broad national perspective to this study, setting the war in the context of both Florida and US military history and Indian policy.