It occurred in 1364 between an expeditionary force of the Ottomans and a Serbian army that also included crusaders, led by king Louis I of Hungary, sent by the Pope.
With the encouragement and efforts of the Pope Urban V, the Principality of Wallachia and the Ban of Bosnia agreed to send some troops to support that allied force.
Lala Şahin Paşa appointed “Hacı İlbey” to be the commander of an expeditionary force that was supposed to monitor and slow down the allied army.
Ottoman akinjis attacked the allied camp in the darkness of night, and they each carried two torches for the purpose of deceiving the enemy into thinking that they had double their actual numbers.
The trick worked, and this surprise attack threw the allied army into a panic given that they were drunk or asleep because of the feast.
Most of the allied troops tried to retreat back to the road where they came from, though many of them were drowned in the Maritsa river while trying to swim to the opposite side.
At the instigation of Pope Urban V, a crusading army of Hungarians, Serbians, Bosnians and Wallachians was formed and in 1364 it set forth to recapture Adrianople.
There at dawn on September 26, 1371, a greatly inferior Turkish force surprised them and slaughtered large numbers...[2]There is no single record of this battle in Serbian and Hungarian sources.
Louis signed a treaty with Emperor Charles and Rudolf IV of Austria in Brno in early 1364, which ended their conflicts.