The Serbian civil war of 1331 broke out following King Stefan Uroà ¡ III's decision not to continue campaigning against the Byzantine Empire when he had the chance following the victory at the Battle of Velbazhd against Bulgaria, alienating much of the nobility, which became divided supporting either Uroà ¡ III or his son, Stefan Duà ¡an.
In 1330, an alliance was formed by Bulgaria and the Byzantine Empire, which sought to invade Serbia. In 1330, Young King Duà ¡an defeated Bulgarian Emperor Michael III Shishman at Velbazhd, after which King Uroà ¡ III appointed his nephew Ivan Stefan at the Bulgarian throne in August.
Uroà ¡ III's decision not to attack the Byzantines after the victory at the Battle of Velbazhd against Bulgaria resulted in the alienation of many nobles, who sought to expand to the south. By January or February 1331, Duà ¡an was quarreling with his father, perhaps pressured by the nobility. According to contemporary pro-Duà ¡an sources, evil advisors turned Uroà ¡ III against his son; he decided to seize and exclude Duà ¡an from his inheritance. Uroà ¡ III sent an army into Zeta against his son, the army ravaged Skadar, but Duà ¡an had crossed the Bojana. A brief period of anarchy in parts of Serbia took place before the father and son concluded peace in April 1331. Three months later, Uroà ¡ III ordered Duà ¡an to meet him. Duà ¡an feared for his life and his advisors persuaded him to resist, so Duà ¡an marched from Skadar to Nerodimlje, where he besieged his father. Uroà ¡ III fled, and Duà ¡an captured the treasury and family. He then pursued his father, catching up with him at PetriÃÂ. On 21 August 1331, Uroà ¡ III surrendered, and on the advice or insistence of Duà ¡an's advisors, he was imprisoned. Duà ¡an was crowned King of All Serbian and Maritime lands in the first week of September.
The civil war had prevented Serbia from aiding Ivan Stephen and Anna Neda in Bulgaria, who was deposed in March 1331, taking refuge in the mountains. Ivan Alexander of Bulgaria feared for the danger of Serbia as the situation there had settled, and immediately sought peace with Duà ¡an. As Duà ¡an wanted to move against richer Byzantium, the two made peace and an alliance in December 1331, accepting Ivan Alexander as ruler. It was sealed with the marriage of Duà ¡an and Helena, the sister of Ivan Alexander.
Duà ¡an later conquered most of the Byzantine Empire, and was crowned Emperor in 1346.