 In 1806, the Fourth Coalition took up arms against him because Prussia became worried about growing French influence on the continent.Napoleon quickly defeated Prussia at the battles of Jena and Auerstedt, then marched his "Grande Armée" deep into Eastern Europe and annihilated the Russians in June 1807 at the Battle of Friedland.France then forced the defeated nations of the Fourth Coalition to sign the Treaties of Tilsit in July 1807, bringing an uneasy peace to the continent.