This book explores the resilience of the Spanish monarchy by uncovering the practices that sustained Philip IV’s monarchy as a major diplomatic power between 1648 and 1660. Adopting an innovative approach, the study does not evaluate whether the resilience of the Spanish monarchy was a success or a failure, but rather how it came about. Based on archival research in Spain, Belgium, Denmark, and Sweden, and drawing on concepts from multilingual historiography and sociology, the book examines in detail the diplomatic missions of Bernardino de Rebolledo in Copenhagen (1648–1659) and Antonio Pimentel in Stockholm (1652–1654), and offers a cultural history of political, organizational, and diplomatic practices in a period marked by uncertainty. The book also considers the confessional dimension of diplomacy and sheds new light on the Spanish monarchy’s relations with the monarchies of Denmark-Norway and Sweden. Providing valuable insights for historians of the Spanish monarchy and for scholars of premodern diplomacy, the book offers the first comprehensive examination of the Nordic dimension of foreign policy under Philip IV, and proposes a new way to understand the Spanish monarchy’s resilience.