Conversation so far:
What was the Battle of Hunayn for Abu Bakr?
The Battle of Hunayn was fought by the Islamic Prophet Muhammad and his followers against the Bedouin tribe of Hawazin and its subsection the Thaqif in the Hunayn valley.
What did Abu Bakr do when the reached the Hunayn valley??
Abu Bakr was commissioned by Muhammad to lead the attack against Ta'if.
Then what did Abu Bakr do after leading the attack against Ta'if?
Abu Bakr advised that the siege might be raised and that God make arrangements for the fall of the fort.

Question: When did the battle happen?
Self-contained rewrite: When did the Battle of Hunayn happen?