Dušan was the eldest son of King Stefan Dečanski and Theodora Smilets, the daughter of emperor Smilets of Bulgaria. He was born circa 1308, or in 1312 in Serbia, but with the exile Dušan's father in 1314, the family lived in Constantinople until 1320, when his father was allowed to return. In Constantinople he learned Greek, gained an understanding of Byzantine life and culture, and became acquainted with the Byzantine Empire. He took a lot interest in arts of war; in his youth he fought exceptionally in two battles: in 1329 he defeated the ban Stephen II Kotromanić during the War of Hum, and in 1330 the Bulgarian emperor Michael III Shishman in the Battle of Velbužd. Dečanski appointed his nephew Ivan Stephen (through Anna Neda) to the throne of Bulgaria in August 1330.