He knew the straits to which Nuremberg and its defenders were reduced, and the impossibility there would be of feeding the new arrivals.
The country round for a vast distance had been long since stripped of provisions, and Gustavus had no course open to him but to march away with his army and leave the city to its fate, or to attack the Imperialists in their stronghold.
On the day after his arrival, the 21st of August, Gustavus marched out and opened a cannonade upon the Imperialists' position, in order to induce Wallenstein to come down and give battle.

Wallenstein was not, however, to be tempted, but kept his whole army busy with the spade and axe further intrenching his position.

The next day the king brought his guns nearer to the enemy's camp, and for twenty-four hours kept up a heavy fire.

The only result, however, was that Wallenstein fell back a few hundred yards on to two ridges, on one of which was the ruined castle called the Alte Veste; the other was known as the Altenburg.

The ascent to these was steep and craggy, and they were covered by a thick forest.