Given the task definition and input, reply with output. Generate a question which can yield the answer mentioned in the input. Generated question must be answered by the answer provided in input, without using any extra knowledge.

Context : Karl Emil Schafer (17 December 1891 -- 5 June 1917) was a German pilot during World War I; he became one of the major German flying aces of the war, with 30 confirmed aerial victories.
Answer : World War I
What was the war that Karl Emil Schafer fought in?