 Just as her young son was assuming the reins of power in 1601, the Saxon chancellor, Nikolaus Krell, who had been spreading the other Protestant doctrine, was overthrown and beheaded in 1601.A more strict adherence to Lutheranism was reintroduced and with it a religious oath.The Thirty Years' War (1618–48) occurred during the reign of Elector John George (1611–56).