The fictional Sanwa-Kai Yakuza clan is, in reality, the Japanese pronunciation of the Triads.
This movie was originally to be released on September 25, 2008, but was delayed because of resistance from the Beijing government.
According to Director Derek Tung-Sing Yee, this movie had been in the planning stages for almost ten years, and was due to start filming in May 2006, but because Chan was busy filming Rush Hour 3 (2007), filming for this movie was delayed. Yee didn't mind waiting until Chan's busy schedule had a slot, as the two are good friends, and because Yee felt Chan was right for the role. On September 26, 2007, it stated on Chan's website that filming was scheduled to begin in "a few weeks" in Japan. Filming began in November 2007.
Steelhead's real name is Zhao Tie, which translates as "Iron Zhao".
This film marks Toru Minegishi's final role after his death in 2008.