The article describes the context in which Caspar von Mster wrote his pamphlet (the so-called "Verteidigungsschrift). The author was landmarshal of the Teutonic Order in Livonia. It was published in 1556 during the time of the so-called "Coadjutors' War. Attention is paid not only to the context of the creation of this source and its author, but to pamphlet's publisher. The fact that it was Johann Daubmann, a typographer of the Prussian Duke Albrecht of Brandenburg-Ansbach, emphasizes the connection between the publication of pamphlets and political interests of the rulers of the neighbouring lands of the Order in Livonia, for example the Duke of Prussia, the King of Poland and Grand Duke of Lithuania. This pamphlet showed internal conflicts in the Teutonic order. A lesser part of this article directs attention to the dating of pamphlet publication. One part of this pamphlet was a letter was written by the landmarshal to the Livonian landmaster Heinrich von Galen. Identified copies of this letter provoke further questions. The first question is about two copies in the archives of the Duke of Prussia. It was made before sending the letter to the Landmaster. Was one of these Mster's draft document, which he later may have given to the Duke of Prussia, and then later to the press? Not less important is the answer to the question of whether this pamphlet drew a wide response or not. One reason for this question is the publication in 1557 of a pamphlet in Daubmann's printing press, but in Latin.