Europe's political balance underwent a major shift in the summer of 1527, when, in a somewhat unplanned operation, mercenary forces of the emperor occupied Rome and drove Pope Clement VII, one of France's principal allies, to capitulate. This development freed Ferdinand — who also acquired the Bohemian throne in late 1526 – from the burden of assisting his brother. By then, Ferdinand had developed a Hungarian policy that was fully in keeping with the interests of his realms. He judged that if Hungary, unable to resist the Ottoman Empire, took action independently of Austria and Bohemia, it might well enter into an alliance with the Ottomans against its western neighbors. It was therefore in the interest of Austria and Bohemia that the Habsburgs gain control of Hungary, by force if necessary.