He is a DAOist deity who is also well thought of by Buddhists. As told in Romance Of The Three Kingdoms, he started life as a mortal vendor of soya bean curd (see TO-FU). But after a heroic incident involving the rescue of a harassed lady and the killing of a tax inspector, he got the taste for battle and embarked on a famous military career with LIU-BEI and ZHANG-FEI, becoming one of the Three Brothers of the Peach Orchard.
Unusually for a God of War, he uses his skill to avoid confrontations if at all possible. A peace-loving deity, he tries to minimize every battle he’s in. (Surely you’ve heard of Kung Few?) But his bravery is legendary.
In one famous tale, his arm was damaged in battle and needed surgery. To the incredulity of on-lookers, he calmly sat playing Solitaire while field surgeons did excruciating things to his tendons. (Just as well Solitaire is a one-handed game.)
When he was finally captured, GUAN-YU was told by Wu, the evil new Emperor, to change sides or face death. GUAN-YU not only refused, he uttered a terrible insult which made even the soldiers blush.
Loyal GUAN-YU knew that changing sides during a war was not only immoral but also against the Law. For his bravery, and because he died defending legal issues, he also became the patron God of Police Officers.
Legend tells that after he died, GUAN-YU appeared before a meditating Master of Buddhism and asked for spiritual guidance. Which was only natural under the circumstances.
Quickly learning the Five Precepts, he became a Buddhist, reached Enlightenment, and now devotes the rest of his Immortality to defending the faith. A completely honorary position, but extremely well-regarded.
Finally, GUAN-YU is also worshipped as a God of Literature — because he managed to read a whole page of Confucius without going cross-eyed.