However, John I married a daughter of Sigismund I of Poland, Isabella, who in 1540 bore him a son. Already dying, the king took an oath from his barons to evade the treaty of Oradea, and his counselor, George Martinuzzi, had the infant John II Sigismund elected as king (1540–1571). Ferdinand I sent troops to take Buda, but they withdrew upon the advance of the Ottoman army. On August 29, 1541 Suleiman I summoned the Hungarian lords to his camp, and while the reception was taking place, his troops occupied the capital of the kingdom. At the same time the sultan assigned the territories of the kingdom east of the Tisa to Queen Isabella and her son in return for an annual tribute.