Süleyman had his eldest son Mustafa strangled in the imperial tent in 1553 after his grand vizier produced a letter in the prince's name to the Shah

Mustafa, born in Manisa in 1515 to Süleyman's first favourite Mahidevran, was the eldest surviving son and popular with the Janissaries. Hürrem Sultan's sons grew up behind him. In 1541 Mustafa was moved from Manisa, near the capital, to distant Amasya. The grand vizier Rüstem Pasha, Hürrem's son-in-law, had a copy of Mustafa's seal cut and sent a letter in his name to Shah Tahmasp of Persia; his men intercepted the Shah's reply and gave it to Süleyman. Mustafa had in fact written to the governor of Erzurum asking for help to take the throne after his father, his "lawful right". Süleyman obtained a fatwa from Ebussuud Efendi. On 6 October 1553 Mustafa rode into his father's camp with 5,000 men, handed over his sword and dagger at the tent, and was attacked by seven mute executioners. Mahmud Ağa finished him with a bowstring. Italian sources say his body was laid on a Persian carpet in front of the tent to show his collusion with the Shah. His money and goods in the camp were seized. His young son Mehmed was strangled in Bursa. The army's anger forced Süleyman to dismiss Rüstem, and a chronogram named the year "Rüstem's trick". Mustafa lies in Bursa's Muradiye complex, in a tomb his half-brother Selim II built.