Actually, this is a map of the Balkans before Ottoman occupation;

This wasn't prior, but during the Ottoman occupation.

The map is dated 1377. I guess it's the beggining of the occupation, some 12 years before the Battle of Kosovo.

Some count it after the Kosovo battle some before, it varies. I personally take it with the loss in the battle of Maritsa.

– Where we lost, because we were drinking that night, nobody took Turks seriously. The Turks attacked us the same night in our sleep. Arrogance was our downfall.