On 15 June 1389 Prince Lazar's Serbian and Bosnian army met Murad I's Ottomans on the Field of Blackbirds. Both rulers died, and the battle's memory outgrew its result.
The Battle of Kosovo was fought on 15 June 1389, St Vitus' Day (Vidovdan), on Kosovo Polje, the Field of Blackbirds, north-west of Priština. An army led by Prince Lazar Hrebeljanović of Serbia, with his son-in-law Vuk Branković and a Bosnian contingent sent by King Tvrtko I, fought the Ottoman army of Sultan Murad I. It is one of very few medieval battles in which both commanders-in-chief died: Murad was killed on the field, and Lazar was captured and executed.
Its immediate military result is genuinely unclear. The first reports to reach the West announced a Christian victory, and the Ottoman army withdrew east after the battle to secure the succession. But Serbia had lost its ruler and many of its nobles, while the Ottoman state passed intact to Murad's son Bayezid I, and within a year Lazar's widow had accepted Ottoman overlordship.
Ottoman expansion into the Balkans had been advancing for a generation. On the Maritsa in September 1371 the Ottomans destroyed the army of the brothers Vukašin and Jovan Uglješa, who ruled the south of the former empire of Stefan Dušan, and the lords of the south became tribute-paying vassals. Northern Serbia, where Lazar built a principality around Kruševac, was spared until the 1380s, when Ottoman raiding reached it: Niš fell in 1386, the year Lazar defeated a raiding force at Pločnik, and in 1388 Tvrtko's commander Vlatko Vuković destroyed another at Bileća in Bosnia.
Murad I, having secured his Anatolian frontier, brought his main army west in 1389 to settle the Serbian question. Lazar was not a king; he styled himself prince (knez) and autocrat of the Serbs. But he had become the leading Serbian ruler, tied by marriage to Vuk Branković, who held Kosovo itself, and allied to Tvrtko I of Bosnia, who had been crowned king of the Serbs and Bosnia in 1377. The army that met Murad was built from these bonds of family and lordship, not raised as a national levy.
No reliable figures survive. Modern estimates put the Christian army at perhaps 12,000 to 25,000 and the Ottoman army at 27,000 to 40,000, ranges that rest on inference rather than records. Lazar held the Christian centre, Vuk Branković the right and Vlatko Vuković's Bosnians the left. Murad commanded the Ottoman centre with his household troops and janissaries, with his sons Bayezid on the right and Yakub on the left, and a screen of archers in front.
Very little about the course of the fighting is secure. The Ottoman chronicle tradition, first written down in the fifteenth century by authors such as Aşıkpaşazade, and the Serbian and Western accounts agree that the Christian heavy cavalry charged early and drove in the Ottoman left under Yakub, and that Bayezid's wing then turned the battle with a counter-attack. The Bosnian and Branković contingents left the field while Lazar's own troops were still fighting, and Lazar was taken prisoner.
Murad's death was the event every source recorded. The earliest Western account, a letter written in October 1389 by the Florentine chancellor Coluccio Salutati to Tvrtko I, says that twelve Christian lords cut their way through to the sultan and that one of them killed him. Ottoman writers tell of a Serbian noble who pretended to desert and stabbed Murad when he was brought before him. Neither names the killer; the name Miloš Obilić comes only from later Serbian tradition. Bayezid, proclaimed sultan on the field, had his brother Yakub strangled, the first recorded fratricide at an Ottoman accession, and had Lazar and the captured Serbian lords executed.
The Ottoman army returned to Anatolia with its new sultan, and in Florence and Paris the battle was celebrated as a Christian triumph. The appearance misled. In 1390 Lazar's widow, Princess Milica, accepted vassalage on behalf of their young son Stefan Lazarević, sent tribute and troops to Bayezid, and gave her daughter Olivera to him in marriage.
Stefan Lazarević became one of the sultan's most valuable vassals, leading Serbian knights for Bayezid at Rovine in 1395, at the Battle of Nicopolis in 1396 and at Ankara in 1402. Vuk Branković held out longest, lost Kosovo to the Ottomans by 1392 and died their prisoner in 1397. The Serbian state survived as a vassal despotate until the fall of Smederevo in 1459.
Lazar's body was taken to his foundation, the monastery of Ravanica, and within a few years he was venerated as a martyr. Church writers presented his death as a choice of the heavenly kingdom over the earthly one, a theme that became the core of the Kosovo cycle of oral epic songs. The same tradition made Vuk Branković the traitor who abandoned the field. Contemporary sources do not support the charge: his troops withdrew once the battle was lost, and he resisted the Ottomans for two years longer than Lazar's heirs.
In the nineteenth century the songs, collected and published by Vuk Karadžić, made Kosovo the central event of Serbian national memory, and Serbian soldiers who took the region in 1912 were told they were avenging it. The battlefield holds two monuments of that long afterlife: the türbe over Murad I's entrails, whose body was carried to Bursa, and the Gazimestan memorial tower of 1953, where Slobodan Milošević addressed a vast crowd on the 600th anniversary in 1989.