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.

In July 1551, at Martinuzzi’s instigation, Isabella ceded Transylvania and the part of Hungary that remained in her hands to Ferdinand, in exchange for the towns of Ratibor and Oppeln in Silesia, and the Austrian troops, under the command of the Spaniard Castaldo, took possession of these territories.[279] When Solyman heard this news, he summoned Malvezzi before him, who pledged his life that there was no ground for this report; but, as he could not give satisfactory explanations, and fell back on the insufficiency of his instructions, he was thrown into prison in the Black Tower of the Castle of Anatolia on the Bosphorus,[280] the Sultan excusing this violation of international law by the argument that an ambassador was a hostage for the good faith of his master, and should suffer for any breach of it. From this incident it appears that the post of ambassador at the Porte was by no means unattended with danger.

Ferdinand rewarded Martinuzzi by procuring for him a Cardinal’s hat, and appointing him Archbishop of Gran. Not content with these dignities, that wily politician made overtures to the Turks, with the object of gaining the sovereignty of Transylvania and Hungary for himself; but he was assassinated by Castaldo’s officers acting under Ferdinand’s orders, or, at any rate, with his connivance, at Alvincz, December 18, 1551.

In 1552 the Turks recommenced their attacks on Hungary, which were attended with almost uniform success. In February they gained a victory at Szegedin; in April, Wessprim was taken by Ali, the Pasha of Buda; and in July Temeswar fell. Its capture was followed by the loss of the rest of the Banat. On August 11, Ali Pasha defeated an army of Ferdinand’s at Fülek, to the north of Buda, Sforzia Pallavicini was taken prisoner, and Sbardellatus Dudich, the Bishop of Waitzen, whom Busbecq calls by mistake the Bishop of Fünfkirchen, was killed.[281] Erlau, however, was besieged by Ali unsuccessfully.

In April 1552, Ferdinand wrote to Roostem, the Grand Vizier, asking for Malvezzi’s release, and for a safe conduct for two more envoys. In consequence, Malvezzi was removed to the Seven Towers, and his allowance was increased; but he was still kept in close confinement.

Fortunately for Ferdinand at this critical juncture, a Persian invasion and the Sultan’s domestic troubles created a diversion in his favour. In 1553 the Sultan, on account of the mutinous disposition of the army, which had been sent to defend Armenia against the Persians, was obliged to take command of it in person. The most notable event of the campaign was the tragical end of Mustapha, Solyman’s eldest and most promising son. The story of his cruel murder is narrated in pathetic words by our author in his first letter,[282] though he is mistaken in placing the scene of it near Amasia, as Eregli, in Karamania, where it really happened, is about 250 miles from that city. To appease the indignation of the soldiery at the death of their favourite, the Grand Vizier Roostem was deposed, and his office conferred on Achmet Pasha. Busbecq, during his visit to Amasia, in 1555, witnessed the conclusion of peace between the Sultan and the Shah.

The Persian war relieved for a time the pressure on Hungary. Solyman granted a six months’ armistice, and Francis Zay and Antony Wranczy or Verantius, then Bishop of Fünfkirchen, and afterwards Bishop of Erlau, were sent as envoys to Constantinople.[283] They arrived in August. They were instructed to offer a tribute of 150,000 ducats for Hungary Proper, and 40,000 for Upper Hungary and Transylvania. The Viziers, however, told them that the abandonment of all claims to Transylvania was an indispensable preliminary to opening negotiations. Malvezzi was accordingly released, and sent to Vienna to receive further instructions from Ferdinand; and it was arranged that the peace should be prolonged for five years, and that on account of the loss of territory Ferdinand had sustained in Hungary the annual present or tribute should be reduced to 15,000 ducats. The peace was not to be ratified till Malvezzi’s return, but the truce was prolonged in the meanwhile.