In January 1454, the year that Casimir IV was married to Elisabeth Habsburg, the Prussian faction asked Casimir IV and protection by the Kingdom of Poland. Casimir asked the Prussian Confederation for a more formal petition. On 4 February 1454, the Secret Council of the Prussian Confederation sent a formal act of disobedience to the Grand Master. Two days later the confederacy started its rebellion and soon almost all Prussia, except for Marienburg, Stuhm , and Konitz , were free from Teutonic rule. Most of the captured Ordensburg castles were immediately destroyed. On 10 February 1454, the confederacy sent an official delegation to Poland, headed by Johannes von Baysen. By 20 February, the delegates were in Kraków and asked Casimir to bring Prussia into the Polish kingdom. After negotiating the exact conditions of incorporation, the king agreed and delegates of the Prussian Confederation pledged allegiance to Casimir on 6 March 1454. On the same day, the king agreed to all the conditions of the Prussian delegates — for instance Thorn demanded the destruction of the Polish city of Nieszawa — giving wide privileges to the Prussian cities and nobility. Three days later, Johannes von Baysen was named as the first governor of Prussia. After 15 April, most of the Prussian estates, with the exception of the Prince-Bishopric of Warmia, pledged allegiance to their new ruler. Poland sent the Grand Master a declaration of war, predated to 22 February. Both sides expected the war to end quickly.
Question: On what date was Johannes von Baysen named the first governor of Prussia?
Answer: 9 March 1454