My dissertation, entitled “Bessarion’s World: Art, Science, and Crusade” examines the patronage and collecting practices of the émigré Basil Bessarion (b. ca. 1403, d. 1472) within the fifteenth-century culture of Crusade in Europe and Byzantium. Basil was born in the kingdom of Trebizond at the eastern end of the Black Sea and immigrated to Rome, Italy in 1442, when he converted from Eastern Orthodoxy and was appointed a cardinal in the Catholic Church. He lived in Italy for over thirty years, during which time he amassed an impressive collection of portable objects, ranging from illuminated manuscripts and early printed books to relics, reliquaries, silks, icons, and liturgical objects. I present the thesis that Basil’s patronage of the arts and sciences was fueled by two closely related endeavors: first, the cardinal’s lifelong travels through the Byzantine world and Europe as a diplomat and preacher for Crusade; and second, his fervent desire to launch a Crusade to reclaim territories lost to Mehmed II (r. 1444-46, 1451-81) and his Ottoman army. Specifically, I argue that Basil acquired works of art for his collection in Rome in order to use them as instigations to Crusade and a moral mandate for Christian princes to take up the Cross and participate in a holy war against the Ottomans.