The first towns in Ostrobothnia were established in the 17th century, obtaining prominence through the import of pine tar, which was essential for the maintenance of the wooden ships of the period. During the Great Northern War the province was occupied from 1714–1721 by Russian troops, along with the rest of Finland. In Ostrobothnia the troops engaged in the creation of a wide strip of no-man's land between occupied Finland and Sweden proper. Northern Ostrobothnia suffered most heavily, losing a fourth of its population due to the ravages of war.