The Royal Prussian Army served as the army of the Kingdom of Prussia. It became vital to the development of Prussia as a European power.

The War of the Fourth Coalition was a war spanning 1806–1807 that saw a multinational coalition fight against Napoleon's French Empire, subsequently being defeated. The main coalition partners were Prussia and Russia with Saxony, Sweden, and Great Britain also contributing. Excluding Prussia, some members of the coalition had previously been fighting France as part of the Third Coalition, and there was no intervening period of general peace. On 9 October 1806, Prussia declared war on France and joined a renewed coalition, fearing the rise in French power after the defeat of Austria and establishment of the French-sponsored Confederation of the Rhine in addition to having learned of French plans to cede Prussian-desired Hanover to Britain in exchange for peace. Prussia and Russia mobilized for a fresh campaign with France, massing troops in Saxony.