Gustav Eriksson was appointed "hövitsman". The rebel force he led grew. In February 1520 it consisted of 400 men, mainly from the area around Lake Siljan. The first big clash in the Dissolution of Kalmar Union that now started, took place at Brunnbäck's Ferry in April, where a rebel army defeated an army loyal to the king. The sacking of the city of Västerås and with it controlling important copper and silver mines gave Gustav Vasa resources and supporters flocked to him. Other parts of Sweden, for example the Götaland provinces of Småland and Västergötland, also saw rebellions. The leading noblemen of Götaland joined Gustav Eriksson's forces and, in Vadstena in August, they declared Gustav regent of Sweden.