Conversation so far:
Where did William F. Buckley Jr. go to school?
Alma mater. Yale University.
Where did William F. Buckley Jr. go to high school?
Millbrook School in Millbrook, New York
When did William F. Buckley Jr. join the military?
1944
How long did William F. Buckley Jr. serve in the military?
Years of service 1944–1946
When did William F. Buckley Jr. join the CIA?
In 1951, along with many other Ivy League alumni, Buckley was recruited into the Central Intelligence Agency (CIA)

Question: How long was he in the CIA?
Self-contained rewrite: How long was William F. Buckley Jr. in the CIA?