Ottoman Empire and one of the last crusades

Sources i used for this video: 

https://www.britannica.com/place/Ottoman-Empire/Osman-and-Orhan

https://www.youtube.com/watch?v=v_0-Vc7uA4g&list=PLaBYW76inbX5BKGRPzlqdztQySZmJLjJt&index=2

 Following the Ottoman invasion on Europe the next step in their conquest will be the beginning of the war against Hungary and Wallachia. As the war with Serbia was won, the sultan (Bayezid I) had a new vassal which was ready to support Ottomans in their wars. After seing the Serbian defeat, balkan leaders decided to attack at a city named Nicopolis by the banks of the Danube river. These lands didn't belong for a long time to the christians as the sultan reacted swiftly. The Ottomans regained their lands and even started organizing raids into Wallachia. 

As Hungarian king (Sigismund) was sure that they needed help with the Ottomans, he called for a crusade. This call was met with a great support as knights Hospitaller, from France, England, Poland, Venice answered. The Ottoman forces met crusaders again at the city of Nicopolis. The sources varie about the enemy numbers, but most of them say that both of the battling forces had around 25 thousand men. The battle was lost by the crusaders, as many of them were young and didn't listen to their commanders, which led to Ottomans surrounding the christian army. Ottoman victory in that battle made it inevitable to stop sultan's invasion towards Europe.