Finally, on 18 February 1529, Charles V, deeply alarmed by the Ottoman progression towards Vienna, again sent a letter from Toledo to Shah Ismail, who had died in 1524 and had been replaced by Shah Tahmasp, pleading for a military diversion. His ambassador to the Shah was the knight of Saint John de Balbi, and an alliance was made with the objective of making an attack on the Ottoman Empire in the west and the east within the following year. Tahmasp also responded by expressing his friendship to the Emperor. A decision was thus taken to attack the Ottoman Empire on both fronts, but Balbi took more than one year to return to the Persian Empire, and by that time the situation had changed in Persia, as Persia was forced to make peace with the Ottoman Empire because of an insurrection of the Shaybanid Uzbeks.