Murad II
In 1439 Ottoman forces led by Sultan Murad II attacked the Serbian Despotate. Serbian Despot Đurađ Branković fled to Hungary to seek support for the defense of his realm, organized by his son Grgur. During the siege of Smederevo (the Despotate's capital city) in 1439, Murad II ordered the marcher-lord Ishak-Beg, who was returning from Mecca, to join forces with Hadım Şehabeddin and besiege Novo Brdo.