The cause of this war was the invasion of Poland in 1658, by Prince George Rákóczy II of Transylvania without the permission of the Porte. Transylvania had after the Battle of Mohács in 1526 recognized Ottoman suzerainty and paid a tribute to the Porte and were given political and religious autonomy in return. On hearing about Rákóczy's unauthorized war, the Ottomans declared war on their vassal. It was not long before Grand Vizier Köprülü Mehmed Pasha (Vizier 1656–1661) defeated Rákóczy and conquered Transylvania. The new Transylvanian prince, János Kemény, fled to Vienna, seeking Austrian support.