Read this: The Kingdom of Prussia became the leading state of the German Empire after its creation in 1871. However, the Treaty of Versailles following World War I granted West Prussia to Poland and made East Prussia an exclave of Weimar Germany (the new Polish Corridor separating East Prussia from the rest of Germany), while the Memel Territory was detached and was annexed by Lithuania in 1923. Following Nazi Germany's defeat in World War II in 1945, war-torn East Prussia was divided at Joseph Stalin's insistence between the Soviet Union (the Kaliningrad Oblast in the Russian SFSR and the constituent counties of the Klaipėda Region in the Lithuanian SSR) and the People's Republic of Poland (the Warmian-Masurian Voivodeship). The capital city Königsberg was renamed Kaliningrad in 1946. The German population of the province was largely evacuated during the war or expelled shortly thereafter in the expulsion of Germans after World War II. An estimated 300,000 (around one fifth of the population) died either in war time bombings raids or in the battles to defend the province.[citation needed]

What year did the Kingdom of Prussia become the leading state of the German Empire?
What is the answer? (If it cannot be answered, return "unanswerable")
1871