 Brandenburg-Prussia benefited from his policy of religious tolerance and he used French subsidies to build up an army that took part in the 1655 to 1660 Second Northern War.This ended with the treaties of Labiau, Wehlau, Bromberg and Oliva; they removed Swedish control of the Duchy of Prussia, which meant he held it direct from the Holy Roman Emperor.In 1672, Frederick William joined the Franco-Dutch War as an ally of the Dutch Republic, led by his nephew William of Orange but made peace with France in the June 1673 Treaty of Vossem.