Servia had already become a vassal state of the Turks, and was compelled to swell with her army the power of the mightiest foe to Christianity. The last victory won by the Servians over the Turks was in 1387, when they mowed down two thirds of the Turkish army, numbering 20,000 men. Sultan Murad invaded Servia in 1389 to avenge the disgrace of defeat. He was met in June by Lazarus, the last independent Prince of Servia, on the Kosovo (blackbird) field, called in Hungarian the Rigómezö. The engagement was a bloody one, and disastrous to the rulers on both sides. Sultan Murad received his death wound from the dagger of a Servian soldier, whilst Prince Lazarus was delivered by his own son-in-law, Vuk Brankovitch, into the hands of the Turks and into the jaws of certain death. With Lazarus was lost the independence of Servia, and his scattered army fled in dismay from the ill-fated battle-field. This victory had brought the Turks one step nearer to the borders of Hungary, and added further to the fear of their victorious arms in that Bajazet, the successor of Murad, surnamed the “Lightning,” was known to be eager for new conquests. Two years after the battle of Kosovo we find the Turks already on Hungarian soil. Sigismund tried, at first, negotiations. Viddin, Nicopolis, and Silistria, which belonged to Hungary under Louis the Great, had recently fallen into the hands of the Turks. Sigismund sent an embassy to Bajazet calling upon him to surrender these cities to their rightful owner. The sultan received the embassy at Brussa, and, conducting them into a hall ornamented with arms and weapons of every description, he pointed at these, saying: “Go back and tell your king that, as you see for yourself, I have a good enough title to these lands.” Sigismund rightly understood this to be a declaration of war. He at once summoned the chivalry of Europe to take part in a crusade against the infidels, and entered into an alliance with Manuel II., the Emperor of the East. Many knights from England, France, and Italy responded to the call.