Philip of Hesse wanted to capitalize politically on the expansion of Protestantism to form a defensive alliance between the Lutherans and the Zwinglians. Philip understood that there could be no political alliance without theological agreement, so he proposed that Zwingli and Luther meet face-to-face at his castle in Marburg (October 1529) to resolve theological differences and thus establish the basis for a political alliance. Philipp Melanchthon, on the other hand, feared that a political alliance