Detailed Instructions: Generate a correct and concise answer for the question based on the words in the context.
Problem:Context : Hans Howaldt (12 November 1888, Kiel -- 6 September 1970) was a successful and highly decorated German U-boat commander in the Kaiserliche Marine during World War I and also active in World War II. By the end of World War I he was promoted Kapitanleutnant.
Question : In which war did Hans Howaldt fight?
Solution:
World War I