Final answer:
The declaration of the unified German Empire was immediately led by the Franco-Prussian War.
Step-by-step explanation:
The event that immediately led to the declaration of the unified German Empire was the Franco-Prussian War. This war took place in 1870-1871 and resulted in a German victory, leading to the creation of a unified German state. The signing of the Treaty of Frankfurt on May 10, 1871, officially established the German Empire.
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