After this, Huguenots (with estimates ranging from 200,000 to 1,000,000) fled to surrounding Protestant countries: England, the Netherlands, Switzerland, Norway, Denmark, and Prussia — whose Calvinist Great Elector Frederick William welcomed them to help rebuild his war-ravaged and underpopulated country. Following this exodus, Huguenots remained in large numbers in only one region of France: the rugged Cévennes region in the south. In the early 18th century, a regional group known as the Camisards who were Huguenots rioted against the Catholic Church in the region, burning churches and killing clergy. It took French troops years to hunt down and destroy all the bands of Camisards, between 1702 and 1709.