In this article, the author attempts to establish the circumstances and meanings of the texts of the 1240s and 1250s, concerning the division of the Prussian lands, which the Bishop of Prussia along with the Teutonic Order had signed with the papal legate William of Modena. This agreement sub-divided the Prussian lands with a ratio of 2:1 in favour of the Order and according to the author’s findings came to fruition in 1232, during the forgotten Prussian mission of Wilhelm of Modena in autumn of this year. It was accompanied by a second agreement, in which, in exchange for the Bishop’s acceptance of the unfavourable division of Prussia, it was agreed to increase his property rights in the Kulmerland. This arrangement was the first agreement between Christian and the Teutonic Order to divide all the Prussian lands, for granting Christian of Rubenicht from the start of 1231, under which the Bishop gave the Teutonic Order a third of their Prussian lands, encompassed only the lands acquired by the Bishop, to come into his possession by voluntary means from the converts of Prussia and not on Prussian lands which were to become the targets of conquest. The partitioning of autumn 1232 proved to have far-reaching consequences in the history of the Teutonic Order State in Prussia, for it became a model for regulating the division of the Prussian territories between the bishops and the Order made by William of Modena in the Act of 28th July 1243.