The last years of Mazarin's life, between 1658 and his death in 1661, were marked by a series of major diplomatic victories, including the marriage of Louis XIV. In 1658, after long and intense preparation, Mazarin unveiled the League of the Rhine, a new group of fifty small German principalities which were now linked by a treaty with France. They promised not to allow enemy forces pass through them to invade France. This treaty weakened both the old Holy Roman Empire and the Austrian Empire of the Habsburgs, This gave a new measure of security to France's eastern border. In the same month, Marshal Turenne decisively defeated the army of Condé at the Battle of the Dunes in Flanders. This marked the end of the threats to France from the north, from the Spanish Netherlands.