Conversation so far:
What was the Mercury Theatre on the Air?
Welles and Houseman founded their own repertory company, which they called the Mercury Theatre.
What did this company do?
The Mercury Theatre opened November 11, 1937, with Caesar, Welles's modern-dress adaptation of Shakespeare's tragedy Julius Caesar -.
How did the play do?
After the theatrical successes of the Mercury Theatre.
What happened next in their business?
The Mercury Theatre's radio adaptation of The War of the Worlds by H.
G.
Wells October 30, 1938, brought Welles instant fame.

Question: How successful was it?
Self-contained rewrite: How successful was The War of The Worlds?