Wars cost money, and this has been the case since ancient times. In the 13th century, when wars were primarily religious conflicts, the financing stemmed from papal crusade taxes, which were collected directly by the Church. Beginning with their first appearance under Pope Innocent III, Gottlob analyzes the origin and legality of papal crusade taxes in his well-researched study, describes theories of ecclesiastical property, and examines the entire 13th century through intensive source studies in relation to the political history of church taxation. In a further extensive section, the author also describes the administrative forms of tax collection, introduces the tax authorities of the time, and analyzes the collection practices of that era. Adolf Gottlob (1857-1930), a doctoral historian, was a professor of modern and ancient history at the university from 1908.