Conversation so far:
When did Pappy Boyington become a prisoner of war?
Pappy Boyington was captured as a prison of war in 1945.
Where was Pappy Boyington held as a prisoner of war?
Pappy Boyington spent some 20 months in Japanese prison camps. After being held temporarily at Rabaul and then Truk, he was transported to Ōfuna and later to Ōmori Prison Camp.
How long was Pappy Boyington held as a prisoner of war?
Pappy Boyington was held prisoner for about 20 months.

Question: When was he rescued?
Self-contained rewrite: When was Pappy Boyington rescued from being a prisoner of war?