The second took place following the Varna Crusade when one group sought to eliminate the threat posed by Skanderbeg.  
The second took place following the Varna Crusade when one group sought to eliminate the threat posed by Skanderbeg.  Janos Hunyadi came to the aid of Skanderbeg, but was defeated on the same ground where Milosh Obilic had stabbed Murad I with a poisoned dagger.  However, Murad's son, Bayezid I, took command of the Ottoman forces and smashed the army of Prince Lazar on the famed Field of Blackbirds.  FTP, give the common name of these two battles, fought in 1448 and 1389 in what is today a secessionist Albanian province of Serbia.
The second took place following the Varna Crusade when one group sought to eliminate the threat posed by Skanderbeg.  
Battle of Kosovo