John Sigismund invaded Upper Hungary on the sultan's order on 28 July. However, when Suleiman died during the Siege of Szigetvár on 6September, Sokollu Mehmed Pasha ordered John Sigismund to return to Transylvania. In a letter written about this time to Cosimo I, Duke of Florence, the mercenary Giovanandrea Gromo described John Sigismund as "extremely benevolent, gracious, subtle in thought, wise, level-headed, industrious [and] brave". Gromo mentioned that John Sigismund spoke Latin, Italian, German, Polish, Hungarian and Romanian well, and could also speak Greek and Turkish.