In this chapter, the diffusion of nationalism and nationalist warfare from the French Revolution to Prussia during and after the Liberation Wars are explored. Prior to the Napoleonic Wars, the nationalist movement in Prussia was limited to few intellectuals and closely linked to the overcoming of monarchic rule and the introduction of democratic representation. Yet, after the defeat of Napoleon, nationalist political discourse as well as nationalist forms of warfare became dominant. Two competing hypotheses are put forward to explain this change, focusing on two different types of diffusion: first, according to the “social movement” hypothesis, the French occupation during the Napoleonic Wars has led to an outbreak of collective emotions of humiliation and pan-German solidarity, resulting in the creation of pan-German militias and other grassroots movements of nationalist resistance. Second, according to the “political elites” hypothesis, especially Prussian leaders deliberately studied and emulated the French model of nationalist warfare in order to instigate popular resistance and mobilize military resources for the “Liberation Wars”. With traditional resources of political legitimacy durably shattered by 1815, political leaders throughout all German states, including those previously allied to France, focussed on the promotion of German patriotism as a way to restore their authority and enable reforms toward more modern yet authoritarian nation-state structures. It is argued that the very limited resonance of grassroots nationalist uprisings before the Liberation Wars suggest that the diffusion of nationalism is primarily the result of an elite-driven, emulative diffusion mechanism.