Conversation so far:
When did Jo Stafford sign with Capital records?
She subsequently became the first solo artist signed to Capitol after leaving the Pied Pipers in 1944.
What was the USO?
Stafford's tenure with the United Service Organizations (USO) during World War II--which often saw her perform for soldiers stationed in the U.S.

Question: What role did she play?
Self-contained rewrite: What role did Jo Stafford play in the United Service Organization (USO) during World War II?