Ferdinand then claimed that, according to the terms of the treaty, he should be placed in possession of the whole of Hungary; but Isabella, as guardian of her infant son, and the party opposed to Ferdinand, under the leadership of Martinuzzi, Bishop of Gross Wardein, refused to adhere to the treaty, caused the infant to be crowned, and appealed to the Sultan for protection. Ferdinand then entered the country, and besieged Buda, which was relieved by the Pasha of Belgrade. Solyman again invaded Hungary in 1541. On August 29 his troops occupied the gates of Buda, and he annexed that city to his dominions, making it the seat of a Pashalic, and placing a strong garrison in it. He declared, however, that he held it merely in trust for John Sigismund during his minority, and in the meantime appointed the latter Sanjak-bey of Transylvania, under the regency of Martinuzzi and Petrovich. The House of Zapolya held, in addition to Transylvania, most of the country to the north as far as the river Theiss. In 1543 Solyman again invaded Hungary, and took the cities of Gran and Stuhlweissenburg, or Alba Regia, the former being the primatial see of Hungary, and the latter the burial-place of her Kings. At the end of 1544, Jerome Adorno, provost of Erlau, was sent by Ferdinand as internuncio to Solyman, with John Maria Malvezzi, a member of a noble family of Bologna, as secretary; but he died shortly after his arrival at Adrianople, in March 1545. Malvezzi, aided by Nicholas Sicco, who was sent by Ferdinand as a new ambassador, and Veltwick, the ambassador of Charles V., then undertook the management of the negotiations, and concluded in November an armistice for eighteen months between Solyman on the one side, and Ferdinand and Charles on the other.[277] This was followed, in June 1547, by a peace for five years, in which the Emperor, the Pope, France, and Venice were included, on the basis of _uti possidetis_, Ferdinand paying the Sultan 30,000 ducats a year, part of which sum was an equivalent for the territories of some of the nobles, who had formerly adhered to the Turkish side, and had afterwards gone over to Ferdinand, and part was termed by him a present, but was more justly considered by the Turks as tribute for the portion of Hungary which still remained in his possession. The Sultan’s motive for concluding this treaty was his desire to turn his arms against Persia. Elkass Mirza, a brother of Shah Tahmasp, the reigning monarch, had taken refuge at his court in 1547,[278] and in 1548 Solyman led his troops into Persia, and obtained considerable successes. In the following year Elkass was captured by his brother in an expedition he had undertaken, and was confined in a fortress for the rest of his life.