Battle of Kosovo
Serbs and Ottomans each lose their ruler in one day

On 15 June 1389 Prince Lazar's army met that of Sultan Murad I; both rulers died, Murad stabbed by the Serbian knight Miloš Obilić. Serbia became an Ottoman vassal, and the battle became the central theme of Serbian epic poetry.
Wikipedia (Russian) · Wikipedia (English) · 14th century
Meanwhile around the world (±25 years)
Eastern Europe & Russia
- 1380 Battle of Kulikovo — 9 years earlier
- 1410 Battle of Grunwald — 21 years later
- c. 1411 Andrei Rublev's Trinity — 22 years later
Middle East
- 1402 Battle of Ankara — 13 years later
Africa
- 1377 Ibn Khaldun's Muqaddimah — 12 years earlier
Asia
- 1377 Jikji, printed with movable metal type — 12 years earlier
- 1392 Founding of Joseon — 3 years later
- 1398 Timur sacks Delhi — 9 years later
- c. 1400 Founding of Malacca — 11 years later
- 1405–1433 Voyages of Zheng He — 16 years later
Alive at the time
- Timur (aged 53)
- Sergius of Radonezh (aged 75)
- Murad I (aged 63)
- Ibn Khaldun (aged 57)
- Dmitry Donskoy (aged 39)
- Ashikaga Yoshimitsu (aged 31)
- Andrei Rublev (aged 29)
- Bayezid I the Thunderbolt (aged 29)
- Richard II (aged 22)
- Sigismund (aged 21)