<P> By early 1393 Turnovo Bulgaria's Ivan Shishman, hoping to throw off his onerous vassalage, was in secret negotiations with Sigismund, along with Wallachian Voievod Mircea the Old (1386--1418) and, possibly, Vidin's Ivan Stratsimir . Bayezid got wind of the talks and launched a devastating campaign against Shishman . Turnovo was captured after a lengthy siege, and Shishman fled to Nikopol . After that town fell to Bayezid, Shishman was captured and beheaded . All of his lands were annexed outright by the sultan, and Stratsimir, whose Vidin holdings had escaped Bayezid's wrath, was forced to reaffirm his vassalage . </P> <P> Having dealt harshly and effectively with his disloyal Bulgarian vassals, Bayezid then turned his attention south to Thessaly and the Morea, whose Greek lords had accepted Ottoman vassalage in the 1380s . Their incessant bickering among themselves, especially those of the Greek Morean magnates, required Bayezid's intervention . He summoned a meeting of all his Balkan vassals at Serres in 1394 to settle these and other outstanding matters . Among the sultan's attending vassals were the Thessalian and Morean nobles, Byzantine Emperor Manuel II Palaiologos (1391--1425), and Serbian Prince Lazarevic . At the meeting, Bayezid acquired possession of all disputed territories, and all of the attendees were required to reaffirm their vassal status . </P> <P> When the Moreans later reneged on their Serres agreement with Bayezid, the angered Ottoman ruler blockaded the Morean despot's imperial brother Manuel II in Constantinople and then marched southward and annexed Thessaly . The Duchy of Athens accepted Ottoman overlordship when Turkish forces appeared on its border . Although a massive Ottoman punitive raid into the Peloponnese in 1395 netted much booty, events in the Balkans' northeast saved Morea from further direct attack at the time . </P> <P> 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 . </P>

Examine the rise and spread of the ottoman empire