Prussia's decision to declare war on France marked a significant escalation in the conflict between the two powers and was a response to the expanding influence of Napoleon Bonaparte across Europe. The War of the Fourth Coalition included several nations such as Russia, Austria, and Sweden, uniting against what they perceived as a threat to their sovereignty and territorial integrity posed by Napoleonic France. Following the Treaties of Tilsit and Amiens, many European states were anxious about French ambitions, prompting Prussia to act decisively to preserve its influence and land.

The war began amid a backdrop of heightened tensions in Europe, with Prussia seeking to challenge France's dominance following its impressive military victories. The mobilization included assembling Prussian troops, which were viewed as a necessary defense against French encroachment. Both military and political leaders in Prussia understood that failing to act would mean conceding to French control over Central Europe, thereby compromising their independence.

In the months leading to armed confrontation, Prussia, under the leadership of King Frederick William III and military leaders like Gerhard von Scharnhorst, prepared for warfare. Key military actions commenced shortly after the declaration, leading to battles that would test the resolve of Prussian forces against Napoleon’s well-trained army. The ensuing conflict would lead to a series of battles, most notably the battle of Jena-Auerstedt, which would dramatically alter the power dynamics in Europe and lead to a significant reorganization of Prussian military capabilities and governance in subsequent years.