A figure unfamiliar to most musicologists, Gottschalk of Aachen was a late eleventh-century notary, cleric, polemicist, and composer who served in the chancellery of King Henry IV from 1071 to 1084. A twelfth-century necrology from the royal Marienkirche in Aachen records a donation by Gottschalk for the annual celebration of the feast of the Division of the Apostles, for which he composed a sequence and a sermon. This study reviews the issues that led to a war of words between King Henry IV and Pope Gregory VII, and focuses on Gottschalk's important role in the controversies that divided church and state. It presents a biographical sketch of the royal apologist and a summary of his official and liturgical writings, and argues that the text and music of his sequence for the Division of the Apostles, understood in light of his sermon on the same theme, promote a highly controversial, royalist view of the medieval church.