After seven years of war and the failed Siege of Vienna in 1529, the Treaty of Konstantiniyye was signed, in which John Zápolya was recognized by the Austrians as King of Hungary as an Ottoman vassal, and the Ottomans recognized Habsburg rule over Royal Hungary.

This treaty satisfied neither John Zápolya nor Austrian Archduke Ferdinand, whose armies began to skirmish along the borders.

Ferdinand sent an army of 24,000 men (from Austria, Hungary, Holy Roman Empire, Bohemia, Tyrol, and Croatia) under the command of the Carniolan nobleman Johann Katzianer to take Osijek.

The Ottoman army reached the Austrians near the swamps of Gorjani, near Đakovo and Valpovo on the Drava river.

[2] A reported 20,000 men were killed,[1] including generals Ludwig Lodron and Pavle Bakić.