In the 16th century, the Ottoman Empire posed a great challenge to the empire.

An excerpt from the article 31 facts about Austria

In 1529, the Turks unsuccessfully besieged Vienna, withdrew, but continued to threaten it for the next 150 years. In 1683, the Turks attacked Vienna again, but as a result of King of Poland John III Sobieski's relief from Vienna, they were repelled and driven beyond Belgrade.