Classical Age of the Ottoman Empire
Expansion continued during the first half of the reign of Suleiman I (r. 1520-1566), who conquered first Belgrade (1521) and Rhodes, before invading Hungary in 1526, defeating and killing King Louis II in the Battle of Mohács and briefly occupying Buda. Lacking a king, Hungary descended into civil war over the succession, and the Ottomans gave support to John Zápolya as a vassal prince. When their rivals the Habsburgs began to achieve the upper hand, Suleiman directly intervened by again conquering Buda and annexing it to the empire in 1541. Elsewhere, Suleiman led major campaigns against Safavid Iran, conquering Baghdad in 1534 and annexing Iraq. Ottoman rule was further extended with the incorporation of much of North Africa, the conquest of coastal Yemen in 1538, and the subsequent annexation of the interior.
Suleiman ibn Qutulmish
In 1078, the Byzantine emperor Michael VII sought the help of Suleiman against Nicephorus Botaneiates, the commander of the Anatolic Theme, who had challenged the emperor for the throne. Suleiman intercepted Botaneiates' small force between Cotyaeum and Nicaea, whereupon the usurper persuaded Suleiman to join his rebellion by offering him incentives superior to those of the emperor. Nicephorus' bid for power was successful, and in return for their support Suleiman's Turkmen were allowed to settle on the Asiatic side of the Bosphorus, near Constantinople itself. Two years later, Suleiman lent his support to another pretender, Nicephorus Melissenus. It was the latter Nicephorus who opened the gates of Nicaea to the Turkmen, allowing Suleiman to establish a permanent base. All Bithynia was soon under Suleiman's control, a circumstance which allowed him to restrict communication between Constantinople and the former Byzantine subjects in Anatolia.