he expansion of the Turks caused concern to the Christian sovereigns of the West and in particular to the King of Hungary, Sigismund, who, having fought beside Mircea at the battle of Rovine (1395), had realised the magnitude of the Turkish danger. For this reason, he organised a crusade against the Turks, with the participation of French and German forces, as well as that of Mircea and his army, and reinforcements from Poland, Bohemia, Italy, Spain and England. In addition, the Venetians, after much hesitation, undertook to keep watch over the Straits of Marmara while the Genoese did the same in the Black Sea. The operation, however, that had started out with high hopes was not destined to have a favourable end. During the battle against the troops of the Turkish sultan, which took place on 25 September 1396 at Nikopolis, dissension broke out in the crusaders' camp, which resulted in their defeat. After this battle, the Turks turned against Vidin, which they took, and in 1397 they invaded the Morea, defeated the Byzantines at the Isthmus of Corinth and ravaged the Peloponnese. Constantinople was now surrounded by the Turks, and was living its last free moments.