Setting the scene
The Battle of Nicopolis, fought on September 25, 1396, was the last major crusade of the Middle Ages and a catastrophic defeat for Christendom. After the Ottoman Turks under Sultan Bayezid I had conquered Bulgaria and threatened Hungary, King Sigismund of Hungary appealed for a crusade. Pope Boniface IX proclaimed it, and a large army assembled—perhaps 15,000-20,000 men, including French knights led by John of Nevers (son of the Duke of Burgundy), Burgundians, Germans, and Hospitallers, plus Hungarian and Wallachian forces. The crusaders were confident, inexperienced in Turkish warfare, and disdainful of Sigismund's advice.
What happened
The crusaders besieged Nicopolis (modern Nikopol, Bulgaria) on the Danube. Bayezid marched to relieve it with perhaps 15,000-20,000 Ottomans and Serbian allies. On September 25, the French knights, against Sigismund's plan for a coordinated attack, charged impetuously up a hill against Ottoman light infantry, who retreated, drawing the knights into a trap. The French were then hit by Bayezid's reserve of heavy cavalry and surrounded. The Hungarian and other forces, seeing the French disaster, fled or were overwhelmed. The crusader army was annihilated.
Why it still matters
Nicopolis was a disaster—perhaps 3,000-10,000 crusaders died, and thousands were captured, including John of Nevers, who was ransomed for 200,000 florins. Bayezid executed most prisoners. The defeat ended serious Western attempts to relieve Constantinople and left the Balkans open to Ottoman conquest. It demonstrated Ottoman military superiority and the folly of Western chivalric tactics against disciplined Turkish forces. Nicopolis, like later Varna (1444), showed that crusading zeal without strategy led to catastrophe. The battle secured Ottoman control of the Balkans for 500 years.
Background
The Battle of Nicopolis took place on 25 September 1396 and resulted in the rout of an allied Crusader army, assisted by the Venetian navy, at the hands of an Ottoman force, raising the siege of the Danubian fortress of Nicopolis and leading to the end of the Second Bulgarian Empire. It is often referred to as the Crusade of Nicopolis, as it was one of the last big Crusades of the Middle Ages, together with the Crusade of Varna in 1443–1444. By their victory at Nicopolis, the Turks discouraged the formation of European coalitions against them. They maintained their pressure on Constantinople, tightened their control over the Balkans, and became a greater threat to Central Europe. French and allied knights suffered heavy losses.