In 1806 Napoleon crushed the fearsome Prussian military machine. The humiliation of military defeat forced the Prussian king into much-needed military reform. The new Prussian army that emerged became one of the finest in Europe., due in part to the organizational genius of Scharnhorst and Gneisenau and in part due to Field-Marshal Prince Bl'cher, who drove his regiments to fight with relentless vigor. 

In 1813 Prussia rejoined the war against Napoleonic France and the Prussian army under Bl'cher, although sometimes playing second fiddle to Austria, Russia and Great Britain, was a major force in bringing an end to Napoleon Bonaparte's rule.

The Prussians played a major part in Napoleon's defeat at Waterloos. Prussia's reward was the recovery of her lost territories, as well as the whole of the Rhineland and Westphalia. Prussia therefore emerged from the Napoleonic Wars as the dominant power in Germany.