At this point, the entire Austrian force, including Klenau's column, withdrew into Ulm and its environs and Napoleon himself arrived to take command of the II, V, VI Corps, Ney's Cavalry and the Imperial Guard, numbering close to 80,000 men. Archduke Ferdinand and a dozen cavalry squadrons broke out through the French army and escaped into Bohemia. Again, as he had been at Mantua, Klenau was caught in a siege from which there was no escape, and again, he helped to negotiate the terms, when, on 21 October, Karl Mack surrendered the encircled army of 20,000 infantry and 3,273 cavalry. Klenau and the other officers were released on the condition that they not serve against France until exchanged, an agreement to which they held.