Task: Question Generation
Input (English): Passage: The Siege of Vienna in 1529 was the first attempt by the Ottoman Empire, led by Suleiman the Magnificent, to capture the city of Vienna, Austria. The siege signalled the pinnacle of the Ottoman Empire's power and the maximum extent of Ottoman expansion in central Europe. Thereafter, 150 years of bitter military tension and reciprocal attacks ensued, culminating in the Battle of Vienna of 1683, which marked the start of the 15-year-long Great Turkish War. The inability of the Ottomans to capture Vienna in 1529 turned the tide against almost a century of conquest throughout eastern and central Europe. The Ottoman Empire had previously annexed Central Hungary and established a vassal state in Transylvania in the wake of the Battle of Mohács. According to Arnold J. Toynbee, "The failure of the first  brought to a standstill the tide of Ottoman conquest which had been flooding up the Danube Valley for a century past." There is speculation by some historians that Suleiman's main objective in 1529 was actually to assert Ottoman control over the whole of Hungary, the western part of which  was under Habsburg control. The decision to attack Vienna after such a long interval in Suleiman's European campaign is viewed as an opportunistic manoeuvre after his decisive victory in Hungary. Other scholars theorise that the suppression of Hungary simply marked the prologue to a later, premeditated invasion of Europe.
Output (English): What country had the Ottoman Empire established a vassal state in?