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.
Albert hastily collected an army and marched to the banks of the Danube just in time to witness the capture of Semendria and the massacre of its garrison.

All Hungary was now in terror.

The Turks in overwhelming numbers were firmly intrenched upon the banks of the Danube, and were preparing to cross the river and to supplant the cross with the crescent on all the plains of Hungary.