This volume chronicles Jesuit efforts to engage with Muslim populations in Christian Europe, such as the Moriscos, as well as the work of Jesuit missionaries in Muslim territory, such as Constantinople. It provides insights into the activities of the Society of Jesus along the eastern frontier of the Ottoman Empire, and tracks the careers of individual Jesuits such as Tomás de León and Antonio Possevino. These influential Jesuits devoted much of their lives to addressing the claims of Islam and the pressures applied on Christian Europe by Muslim polities. Some lesser-known Jesuits, such as the translator Ignazio Lomellini, are also profiled.