In 1577 the Goslar citizens signed the Lutheran Formula of Concord. After years of continued skirmishes, they finally had to grant Duke Henry and his son Julius extensive mining rights which ultimately edged out the city council. Nevertheless, several attempts by the Brunswick dukes to incorporate the Imperial city were rejected. Goslar and its economy was hit hard by the Thirty Years' War, mainly by the financial crisis in the 1620s which led to several revolts and pogroms. Facing renewed aggressions by Duke Christian the Younger of Brunswick, the citizens sought support from the Imperial military leaders Tilly and . The city was occupied by the Swedish forces of King Gustavus Adolphus from 1632 to 1635; in 1642 a peace agreement was reached between Emperor Ferdinand III and the Brunswick duke Augustus the Younger. The hopes of the Goslar citizens to regain the Rammelsberg mines were not fulfilled.