It was clear from the onset that Stephen's reign in Serbia would be short-lived. The Ottoman sultan Mehmed the Conqueror considered Stephen's enthronement an unwarranted violation of his own rights, for the Ottomans too considered Serbia their vassal state. Mehmed promptly launched an attack on Smederevo in June, and there was no serious consideration of trying to defend it. King Thomas rushed to his son's aid, trying to divert the Turks by laying siege to their fortress of Hodidjed, in the middle of Bosnia. Aware that Smederevo could not withstand Mehmed's attack, Stephen surrendered the fortress on 20 June. The Ottoman proceeded to annex the rest of the Serbian state to their empire within a year.