This is the third of four volumes which trace the history of the later Crusades and papal relations with the Levant from the accession of Innocent III (in 1198) to the reign of Pius V and the battle of Lepanto (1566-1571). From the mid-fourteenth century to the conclusion of his work, the author has drawn heavily upon unpublished materials, collected in the course of more than twenty palaeographical journeys to the Archivio Segreto Vaticano and the Archivi di Stato in Venice, Mantua, Modena, Milan, Siena, Florence, and the Archives of the Order of the Hospitallers at Malta. Volumes 1, II, and IV are available at www.amphilsoc.org.