Transformation of the Ottoman Empire
Sultan Suleiman I (r. 1520–1566) was the longest-reigning sultan in Ottoman history, but the last years of his reign were characterized by uncertainty over who would be his successor. Suleiman had three sons who could hope to succeed, Mustafa, Bayezid, and Selim. While the latter two were the children of Suleiman's wife Hurrem Sultan, the first was the son of an earlier concubine. Mustafa may have felt that his half-brothers possessed an unfair advantage over him, and thus worked to secure the favor of the military. Perhaps suspecting that Mustafa planned to dethrone him just as his own father had done to his grandfather, Suleiman acted first and in 1553 ordered that Mustafa be executed. The death of Hurrem Sultan in 1558 triggered open conflict between the two remaining candidates, and Selim ultimately emerged victorious. Suleiman further strengthened his son's position by arranging a marriage between Selim's daughter and the influential Sokollu Mehmed Pasha (Grand Vizier 1565–1579). Suleiman died in 1566, while besieging the fortress of Szigetvar in Hungary, bringing Selim to the throne.
List of campaigns of Suleiman the Magnificent
In January 1566 Suleiman, who had ruled the Ottoman Empire for 46 years, went to war for the last time. Although he was 72 years old and suffered gout to the extent that he was carried on a litter, he nominally commanded his thirteenth military campaign. On 1 May 1566, the Sultan left Constantinople at the head of one of the largest armies he had ever commanded. Nikola Šubić Zrinski's success in an attack upon an Ottoman encampment at Siklós, and as a consequence Suleiman's siege of Szigetvár, blocked Ottoman's line of advance towards Vienna. Although an Ottoman victory, the battle stopped the Ottoman push for Vienna that year, since Suleiman died during the siege.