Conversation so far:
What did Don Knotts try first?
Before he entered high school, Don Knotts began performing as a ventriloquist and comedian at various church and school functions.
What did ventriloqui and comedy lead Don Knotts to do after high school?
After high school, Don Knotts traveled to New York City to try to make his way as a comedian.
What did Donm Knotts do after college?
After his college freshman year, Don Knotts joined the U.S. Army.

Question: What did he do for the army
Self-contained rewrite: What did Don Knotts do for the army?