While Bayezid was occupied in Greece, Mircea of Wallachia conducted a series of raids across the Danube into Ottoman territory. In retaliation, Bayezid's forces, which included Serb vassal troops led by Lazarevic and Kralj Marko, struck into Wallachia in 1395 but were defeated at Rovine, where Marko was killed. The victory saved Wallachia from Turkish occupation, but Mircea accepted vassalage under Bayezid to avert further Ottoman intervention. The sultan took consolation for his less than victorious efforts in annexing Dobrudzha and in supporting a pretender, Vlad I (1395–97), to the Wallachian throne. Two years of civil war ensued before Mircea regained complete control of the principality.