Q: 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 : Captain Robert F. R. Lewis (30 January 1826 - 23 February 1881) was an officer in the United States Navy. 
Answer : United States Navy
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
In what military organization did Robert F. R. Lewis serve?