The Turks were at this time becoming the terror of Christendom. Originating in a small tribe between the Caspian Sea and the Euxine, they had with bloody cimeters overrun all Asia Minor, and, crossing the Hellespont, had intrenched themselves firmly on the shores of Europe. Crowding on in victorious hosts, armed with the most terrible fanaticism, they had already obtained possession of Bulgaria, Servia, and Bosnia, eastern dependencies of Hungary, and all Europe was trembling in view of their prowess, their ferocity and their apparently exhaustless legions. Sigismond, beholding the crescent of the Moslem floating over the castles of eastern Hungary, became alarmed for the kingdom, and sent ambassadors from court to court to form a crusade against the invaders. He was eminently successful, and an army of one hundred thousand men was soon collected, composed of the flower of the European nobility. The republics of Venice and Genoa united to supply a fleet. With this powerful armament Sigismond, in person, commenced his march to Constantinople, which city the Turks were besieging, to meet the fleet there. The Turkish sultan himself gathered his troops and advanced to meet Sigismond. The Christian troops were utterly routed, and nearly all put to the sword. The emperor with difficulty escaped. In the confusion of the awful scene of carnage he threw himself unperceived into a small boat, and paddling down the Danube, as its flood swept through an almost uninhabited wilderness, he reached the Black Sea, where he was so fortunate as to find a portion of the fleet, and thus, by a long circuit, he eventually reached his home. Bajazet, the sultan, returned exultant from this great victory, and resumed the siege of Constantinople, which ere long fell into the hands of the Turks. Amurath, who was sultan at the time of the death of Sigismond, thought the moment propitious for extending his conquests. He immediately, with his legions, overran Servia, a principality nearly the size of the State of Virginia, and containing a million of inhabitants. George, Prince of Servia, retreating before the merciless followers of the false prophet, threw himself with a strong garrison into the fortress of Semendria, and sent an imploring message to Albert for assistance. Servia was separated from Hungary only by the Danube, and it was a matter of infinite moment to Albert that the Turk should not get possession of that province, from which he could make constant forays into Hungary.