Final answer:
Germany's rapid support for Austria after the assassination of Archduke Franz Ferdinand exemplifies nationalism, where mutual defense and nationalist sentiments facilitated a cascade leading to World War I.
Step-by-step explanation:
The quick support provided by Germany to Austria following the assassination of Archduke Franz Ferdinand is an example of nationalism. Germany was keen to support its ally to maintain strong nationalist ties and potentially challenge its rivals, Russia and France. The assassination in Sarajevo triggered a series of events and alliances that ultimately led to World War I, showcasing the volatile nature of nationalist sentiments and mutual defense treaties of the time. Nationalism in this context is seen as a force for unity within a nation and as aggression toward others whom the nation perceives as threats or opponents.
Germany's so-called "blank check" to Austria-Hungary, promising unconditional support, ignited the powder keg in the Balkans and involved Europe, and eventually the world, in a catastrophic conflict. This can be seen as a broader effect of nationalist movements, which on one hand sought unity and independence but on the other incited imperial dominance and territorial disputes. Therefore, Germany's rapid alignment with Austria exemplified the nationalist drives of the era that led to large-scale international conflict.