The Fourth Coalition against Napoleon's French Empire is defeated in a war spanning 1806–1807.

Coalition partners include Prussia, Russia, Saxony, Sweden, and the United Kingdom.Many members of the coalition had previously been fighting France as part of the Third Coalition, and there is no intervening period of peace.

In 1806, Prussia joins the coalition fearing the rise in French power after the defeat of Austria.

Prussia and Russia mobilize for a fresh campaign, and Prussian troops mass in Saxony.