The restless and treacherous Ferdinand, despite the peace signed with the Ottoman empire in 1547, is determined to regain control of Transylvania, and finds it intolerable that the Ottoman Pashalik of Buda separates Transylvania from Habsburg-controlled Austrian, or Royal, Hungary.

Isabella, the queen mother of Transylvania’s young vassal king, protests to the Ottoman Porte in 1551 that Martinuzzi has assumed too much power and has attempted to have her surrender Transylvania in exchange for equivalent Austrian areas, especially Silesia.

Ferdinand besieges Lippa, the Transylvanian capital, in order to ensure this exchange, for which Martinuzzi acts as go-between.

Martinuzzi finally concludes the agreement with Ferdinand in 1551, by which he continues to be governor of Transylvania and is rewarded with the archbishopric of Esztergom (Gran) and a cardinal's hat at sixty-nine.

Süleyman dispatches an Ottoman army to Lippa and establishes a garrison there.

To forestall attack by the Turks, Martinuzzi resumes payment of tribute to the Porte in early December.

Ferdinand, however, suspects the cardinal's loyalty and has him killed on December 17.

Taking the responsibility of the murder on himself, he sends to Pope Julius III an accusation of treason against Martinuzzi in eighty-seven articles.

After long hesitation, and hearing one hundred and sixteen witnesses, the pope will exonerate Ferdinand of blame.