Why does Tyll take a job in the coal mines outside Brno in the novel, Tyll?

Below the town of Brno (in the modern-day Czech Republic) Tyll volunteers to work to avoid conscription into the military. Tyll, already an established celebrity, originally volunteered to work the mines because he (along with the other hapless men in the mine shafts) figured Brno was safe, that the invading Swedish army would most likely head to Vienna and the Kaiser.