Legend says the general entered monastic life in his later years.
Tips
culture
空门 (the Empty Gate) is a Buddhist term - Buddhism teaches that all phenomena are empty (空), so entering monkhood means passing through that gate. The phrase is dramatic and usually implies retreat after personal upheaval.
memory
遁 (to flee/withdraw) + 入 (enter) + 空门 (empty gate) - literally "flee into the empty gate." Picture someone walking away from worldly noise into a silent temple.
