Conversation so far:
What were the USO tours?
The USO tours were tours to provide morale and recreation services to U.S. uniformed military personnel.
When did he start the USO tours?
Overseas shows began in November 1941 with a tour of the Caribbean.
Was Joe E. Brown a soldier in World War Two?
Aged 50 when the US entered World War II, Joe E. Brown himself was too old to enlist.

Question: How would he entertain troops?
Self-contained rewrite: How would Joe E. Brown entertain troops?