This article examines the religious and political worldview of the Scottish minister John Dury during the English Revolution of the mid-seventeenth century. It argues that Dury's activities as an irenicist and philo-semite must be understood as interrelated aspects of an expansionist Protestant cause that included Britain, Ireland, continental Europe, and the Atlantic world. Dury sought to imitate and counter what he perceived to be the principal strengths of early modern Catholicism: confessional unity, imperial expansion, and the coordination of global missionary efforts. The 1640s and 1650s saw the scope of Dury's long-standing vision grow to encompass colonial expansion in Ireland and America, where English and continental Protestants might work together to fortify their position against Spain and its growing Catholic empire. Both Portuguese Jews and American Indians appear in this vision as victims of Spanish Catholicism in desperate need of Protestant help. This article thus offers new perspectives on several aspects of Dury's career, including his relationship with displaced Anglo-Irish Protestants in London, his proposal to establish a college for the study of Jewish learning and “Oriental” languages, his speculation regarding the Lost Tribes of Israel in America, and his cautious advocacy for the toleration of Jews in England.