Jean-Claude Van Damme actually knocked out Bernard Mariano with his elbow. The scene made it into the movie.
This is one of the few films featuring scenes filmed inside Kowloon Walled City before its destruction.
The movie was touted as a true story, but over the years, doubts have arisen about its veracity. Most martial-arts enthusiasts consider Frank Dux' accounts of competing in secret tournaments a complete fiction, along with his claims he was an undercover CIA operative. Some have pointed out that nobody else has confirmed his story, or told their own version. It is now generally accepted that Dux lied his way into Hollywood, and has most likely never competed in a martial arts tournament. According to records obtained through the Freedom of Information Act, Dux was in the US Marine Corps Reserve, and was never posted overseas. The CIA has no record of him ever working with them. His personal brand of martial arts, Dux Ryu Ninjitsu, is also a complete fabrication.
Midway's hit videogame, Mortal Kombat (1992), took huge inspiration from the film and even used a parody of Jean-Claude Van Damme for the character Johnny Cage, who has a similar costume, back story and a familiar split punch. According to game creator John Tobias, they wanted to make a "gritty" game based on the film.
Frank Dux was the fight coordinator for this film. When Jean-Claude Van Damme was cast, Dux announced that Van Damme wasn't nearly in good enough shape, and put him through a 3-month training program. Van Damme, a world-championship martial artist in his own right, called it the hardest training of his life.