The twelfth-century Latin poem called the Relatio metrica de duobus ducibus has never been edited or translated before. On its surface, the poem retells a popular exemplum about an encounter between two warring dukes and a mysterious army from heaven. While retelling the story in verse, however, the poet has greatly expanded his prose source, elaborating its teachings about the importance of intercessions for the dead and introducing wholly new emphases on knightly piety and the benefits of dying for a holy cause. The present book, which offers the first edition, translation, and analysis of the poem, situates the 827-line poem in its literary and historical contexts. The publication of the Relatio metrica should be of interest to scholars of medieval Latin poetry, Cluniac monasticism, and the spirituality of the Crusades.