Detailed Instructions: Given a paragraph, your job is to generate a question that can be answered from the passage. The answer to your question should be a single entity, person, time, etc. that can be extracted from the passage.
Q: Frederick William, Elector of Brandenburg, invited Huguenots to settle in his realms, and a number of their descendants rose to positions of prominence in Prussia. Several prominent German military, cultural, and political figures were ethnic Huguenot, including poet Theodor Fontane, General Hermann von François, the hero of the First World War Battle of Tannenberg, Luftwaffe General and fighter ace Adolf Galland, Luftwaffe flying ace Hans-Joachim Marseille, and famed U-boat captain Lothar von Arnauld de la Perière. The last Prime Minister of the (East) German Democratic Republic, Lothar de Maizière, is also a descendant of a Huguenot family, as is the German Federal Minister of the Interior, Thomas de Maizière.
A:
What German ruler invited Huguenot immigration?