Excerpts from Books and Wikipedia
"The Battle of Nicopolis took place on 25 September 1396 and resulted in the rout of an allied crusader army of Hungarian, Croatian, Bulgarian, Wallachian, French, English, Burgundian, German and assorted troops (assisted by the Venetian navy) at the hands of an Ottoman force, raising of the siege of the Danubian fortress of Nicopolis and leading to the end of the Second Bulgarian Empire." [Wikipedia] "In the late 1300s the Ottoman Turks began their conquest of southeastern Europe. As Turkish armies began to threaten the kingdom of Hungary, a Crusade was called. . . . The Crusaders' mounted men-at-arms charged without order into the solid infantry lines of the Turks, were halted and beaten by counter-attacking cavalry. . . . The Turks built on this victory to complete their conquest of southeastern Europe." [Battles of the Medieval World] Manuel needed help from the outside. Aid finally came from Sigismund of Hungary, ruling in the place of his young wife. . . . In the end, they all advanced to Nicopolis: they had become a formidable force only because Sigismund himself had reinforced their ranks with sixty thousand Hungarians. There, on September 25, Bayezid crushed them."