Blaker Fortress is one of the Norwegian fortresses which were constructed in the period of intense competition among the Baltic powers (Denmark-Norway, Sweden, Russia, Poland and the German states) for northern supremacy. The 17th and beginning of the 18th century was a period of virtually continuous war or preparation for war, as follows: * 1611 to 1613 - Kalmar War * 1618 to 1648 - Thirty Years' War * 1655 to 1658 – Northern Wars * 1673 to 1675 – Fortification Upgrades * 1675 to 1679 – Gyldenløve War * 1700 to 1721 – Great Northern War