The Swedish Empire had the greatest and most numerous copper mines in Europe as it entered into its pre-eminence in the early 17th century as an emerging Great Power. Through poor fiscal policies and in part the Treaty of Älvsborg, Sweden lost control of its reserves of precious metals, primarily silver, of which most had fled to the burgeoning trade economy of Amsterdam. In 1607 the Swedish king Charles IX attempted to persuade the populace to exchange their silver-based currency for a copper-based coin of equal face value, though this offer was not generally taken up. Sweden's large army of the time were paid entirely in copper currency, further issued in large numbers by Gustavus II to finance his war against Ferdinand II of Germany. The face value of the copper coins in circulation now