Combining Iberian and East Asian primary source documents can provide a fresh perspective on sixteenth-century East Asian history. This is particularly true of the Imjin War (1592–98), the largest war in the world during the sixteenth century. Involving China, Korea, and Japan, it attracted close observation from Jesuit missionaries, who wrote a number of as yet largely unstudied accounts of the conflict and its implications for the Jesuit mission. We analyze one such manuscript, which is particularly detailed and unique in its scope: the Relação do fim e remate que teve a guerra da Corea, cross-referenced with Chinese, Japanese, and Korean accounts.