Conversation so far:
Where did Tom Lehrer go to school?
Lehrer earned his Bachelor of Arts in mathematics (magna cum laude) from Harvard University.
Did he go to graduate school?
1946.
He received his MA degree the next year.
Did Lehrer ever join the military?
He was drafted into the U.S.
Army from 1955 to 1957.

Question: What was his rank in the military?
Self-contained rewrite: What was Tom Lehrer's rank in the military?