After a day of rest, on 7 December, Frederick sent half his cavalry with Zieten, chasing Charles's retreating army, now heading toward Königgrätz by Schweidnitz and captured another 2,000 men and their baggage. With the rest of his army, Frederick marched on Breslau. By chasing Charles's army into Bohemia, the Prussians guaranteed the isolation of the Allied garrison holding Breslau. The Austrian general left in command of the city, Lieutenant Field Marshal Salman Sprecher von Bernegg, had a combined force of French and Austrian of 17,000 men. Breslau was a well-fortified city of walls and moats. The Austrians were determined to hold Breslau not only because losing it would cost them control of Silesia and considerable diminution of prestige but also because of the immense quantities of stores that the city held. The Austrian commander, recogniaing his grim plight, posted placards on gallows and poles throughout the city and warned that anyone who spoke of surrender would be hanged immediately. On 7 December, Frederick laid siege to the city, and the future of Austrian control of Breslau and the region looked grim. Indeed, Breslau surrendered on 19–20 December.