Amongst the battles in which Serbs fought for their Ottoman allies were Battle of Rovine, against the Wallachians and Bulgarians, in 1395; Battle of Nicopolis in 1396, where apparently their contingent comprised 5,000 heavy cavalry; and Battle of Ankara in 1402, where Doukas says there were 5,000 "encased in black armor" and Chalkokondyles that there were an unlikely 10,000 (though the Ottoman chronicler al-Anwari says that there were 10,000 Serbs and Wallachians altogether). George Branković even supplied an unwilling contingent of 1,500 cavalry under voivode Jakša according to Konstantin Mihailović, for the final siege of Constantinople in 1453, plus some silver-miners from Novo Brdo whom Sultan Mehmed employed as sappers. On August 11, 1473, the army that marched against Uzun Hasan which resulted in an Ottoman victory in The battle of Otlukbeli included many Christians - Greeks, Albanians and Serbians, in their number.