He was again in Silesia, which was once more seriously threatened by the Austrian forces. His position was anything but a safe one. The Austrians almost surrounded him. On one side was the army of Field-Marshal Daun, on the other that of General Lasci; in front was General Laudon. Fighting day and night he advanced, and finally took up his position at Liegnitz, where he found his forward route blocked, Daun having formed a junction with Laudon. His magazines were at Breslau and Schweidnitz in front, which it was impossible to reach; while his brother, Prince Henry, who might have marched to his relief, was detained by the Russians on the Oder. The position of Frederick was a critical one. He had only a few days' supply of provisions; it was impossible to advance, and dangerous to retreat; the Austrians, in superior numbers, were dangerously near him; only fortune and valor could save him from serious disaster. In this crisis of his career happy chance came to his aid, and relieved him from the awkward and perilous situation into which he had fallen. The Austrians were keenly on the alert, biding their time and watchful for an opportunity to take the Prussians at advantage. The time had now arrived, as they thought, and they laid their plans accordingly. On the night before the 15th of August Laudon set out on a secret march, his purpose being to gain the heights of Puffendorf, from which the Prussians might be assailed in the rear. At the same time the other corps were to close in on every side, completely surrounding Frederick, and annihilating him if possible. It was a well-laid and promising plan, but accident befriended the Prussian king. Accident and alertness, we may say; since, to prevent a surprise from the Austrians, he was in the habit of changing the location of his camp almost every night. Such a change took place on the night in question. On the 14th the Austrians had made a close reconnoisance of his position. Fearing some hostile purpose in this, Frederick, as soon as the night had fallen, ordered his tents to be struck and the camp to be moved with the utmost silence, so as to avoid giving the foe a hint of his purpose. As it chanced, the new camp was made on those very heights of Puffendorf towards which Laudon was advancing with equal care and secrecy. That there might be no suspicion of the Prussian movement, the watch-fires were kept up in the old camp, peasants attending to them, while patrols of hussars cried out the challenge every quarter of an hour. The gleaming lights, the watch-cries of the sentinels, all indicated that the Prussian army was sleeping on its old ground, without suspicion of the overwhelming blow intended for it on the morrow.