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.
Ottoman dynasty
Some early Ottoman Sultans even had to accept the vassal status in the eyes of a foreign overlord. For example, Tamerlane appointed in 1402 the Ottoman Sultan Süleyman Çelebi (deposed in 1411), who was styled "as-Sultan ul-Azam, Sayyid us-Saladin ul-Arab wal Ajam, Malik ur-Rikaab ul-Umam, Ghiyas ud-Daula wa ud-Dunya, Sultan ul-Islam wal-Muslimin, as-Sultan ibni us-Sultan, Hasib-i-Nasib-I-Zaman, Amir ul-Rumelia" (Grand Sultan, Righteous Lord of Arabs, Helper of the State and the People, Sultan of Islam and the Muslims, Sultan son of Sultans, Prince of Rumelia). Again his brother, Mehmed I, who ended the Ottoman Interregnum, also held his post with a fief from Tamerlane; he took the title "Sovereign of the House of Osman, Khan of Khans, Grand Sultan of Anatolia and Rumelia, and of the Cities of Adrianople and Philipopolis". However, the vassalage of the Ottoman Sultanate ended with the death of Tamerlane during the reign of the next Ottoman ruler, Sultan Murad II, who took the style "Sultan ul-Mujahidin, Sovereign of the House of Osman, Khan of Khans, Grand Sultan of Anatolia and Rumelia, and of the Cities of Adrianople and Philipopolis".