It proved difficult for the besiegers to maintain the siege because the city was large and needed a large force to man the circumvallation. In Wallenstein's camp, there were 50,000 soldiers, 15,000 horses and 25,000 camp followers.[2] Foraging to supply such a large static besieging force proved to be extremely difficult. Gustavus' army grew through reinforcements from 18,500 to 45,000 men with 175 field guns, the largest army he ever led in person.[4]
With poor sanitation and inadequate supplies, both sides suffered from hunger, typhus and scurvy. To try to break the deadlock, 25,000 men under Gustavus attacked the Imperial entrenchments in the Battle of the Alte Veste on 3 September but failed to break through, having lost 2,500 men compared to 900 Imperials.[3] Eventually, the siege ended after eleven weeks when the Swedes and their allies withdrew. Disease killed 10,000 Swedish and allied troops, with an additional 11,000 deserters.[3] Gustavus was so weakened by the struggle that he sent peace proposals to Wallenstein, who dismissed them.[3]