Conversation so far:
What did Gary Cooper do in 1925?
In early 1925, Cooper began his film career in silent pictures.
What pictures did Gary Cooper do?
Sergeant York, High Noon, and The Hanging Tree
Did Gary Cooper win any awards for Sergeant York, High Noon, or The Hanging Tree?
Yes, for all films.
Who did Gary Cooper work with?
Some actors Gary Cooper worked with include Jack Holt, Tom Mix, and Buck Jones.

Question: what was his greatest achievement?
Self-contained rewrite: What was Gary Cooper’s greatest achievement?