Reasons for the defeat of all crusades.

First, most of the Crusades, especially the Varna Crusade, were poorly organized. Their leaders, European kings, nobles and generals, often clashed with each other, which interfered with the conduct of military operations. The Crusaders had less forces in the Middle East than the Arabs and Seljuks, and also refused any alliance with a strong Byzantium, whose troops could help them in the fight against Muslim states, due to religious contradictions.