Actor Philip Ng (R) poses for a photo with Bruce Lee enthusiast Jeff Chin (L) at a special screening of BH Tilt & WWE Studios' 'Birth of the Dragon' at the AMC Dine-In Kabuki 8 theater on August 16, 2017 in San Francisco, California. (AFP/Kelly Sullivan)
On a crisp December evening in 1960s California, two men near the peak of their powers locked horns in a battle that would go down in the annals of kung fu mythology.
On one side was a scrawny 24-year-old monk, newly arrived from eastern China, who exuded reserve and modesty despite being one of the fabled Shaolin Temple's most skilled grand masters.
On the other: a brash, street-smart fighter of Chinese heritage but American birth -- also 24 -- who was about to announce himself as the most iconic proponent of unarmed combat in history.
"Birth of the Dragon," which hits theaters on Friday, showcases that epic face-off between Wong Jack Man and Bruce Lee, attempting to shine a light on a secretive and mysterious encounter that changed kung fu.
The handful of witnesses have never agreed on exactly what went down at Lee's gym in Oakland that night -- not the length of the confrontation, nor exactly how many people saw it, nor even who won.
What is undisputed is that the encounter transformed Lee's approach to kung fu, setting him on the path to becoming "The Dragon," a global superstar who introduced the until-then obscure martial art to world.
"My father owns a martial arts school and he has a friend that was actually one of the witnesses," said Chinese-American action star Philip Ng, 39, who plays Lee and believes it was he who triumphed.
"I heard his story and it contradicts some of the stuff that I read. I have my beliefs and my hypothesis about what happened in the fight but one thing that is definite is the fact that after this fight, Bruce Lee evolved his fighting methodology."
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Set against the backdrop of 1964 San Francisco, "Birth of the Dragon" takes its inspiration from the classic movies Lee is known for, such as "Fist of Fury" and the posthumously released "Enter the Dragon."
Legendary Shaolin monk Wong (Xia Yu), arrives in San Francisco to observe the state of kung fu in America and is immediately seen as a threat by Lee, who challenges him to the legendary duel.
Ng decided Lee was too well known for a straight-up impersonation to work, and instead created his own version, anchored on the fighter's distinctive Hong Kong and "1960s San Francisco hippy slang" accent.
The actor was born after Lee's mysterious death from cerebral edema at the age of just 32, but believes he has been preparing, mostly unwittingly, to play the master his entire life.
Ng -- a prolific kung fu movie star in his own right -- became proficient in Lee's Wing Chun style in his native Hong Kong under Wong Shun Leung, the man credited with training Lee.
"He told me a lot of stories about Bruce Lee growing up, outside of kung fu and movies -- things you can't read in books," said Ng.
"And working in Hong Kong for the last 15 years in action movies, I've met a lot of people over the years who were close to Bruce."
Lee was noted for his generosity and sense of fairness, but George Nolfi's movie invokes an arrogant yet gifted upstart who annoyed the Chinese masters with his insistence on teaching kung fu to Westerners and disrespecting its traditions.
Lee's big idea
"He was definitely confident, but you have to be confident to the point of cockiness, because the ideas that he was talking about were very revolutionary and very controversial at the time within kung fu," says Ng.
Lee's big idea -- that style doesn't matter, that it's all about winning -- has been vindicated, says Ng, by the emergence of mixed martial arts as a lucrative spectator sport.
Despite being an expert in Wing Chun, a style emphasizing punches which is particularly devastating at close quarters, Ng says the central fight in "Birth of the Dragon" was the toughest he had ever filmed.
"I've made about 40 movies and TV shows altogether in Hong Kong if you add up my resume. I've never filmed a fight like that. It's a 500 move fight -- 500 moves! The most moves I've done maybe is 300," he told AFP.
Lee's widow Linda, now 72, describes in her 1975 book "Bruce Lee: The Only Man I Knew" how the fight was far too close in her husband's opinion, causing him to abandon Wing Chun.
He went on to invent his own style, Jeet Kune Do, a dazzlingly choreographed mix of many kung fu styles that made him a movie star and popualarized the previously obscure martial art of kung fu.
Wong -- who always insists the victory was his -- later expressed regret over agreeing to fight Lee, putting his acquiescence down to youthful arrogance.
He went on to teach the Northern Shaolin style in San Francisco before retiring in 2005.
Thought to be 77, he now lives in relative obscurity, the only man alive who knows for sure who won the fight that changed kung fu.