Century of the Dragon (1999)

A lawman finds his loyalties put to the test in this action thriller from Hong Kong. Shing (Louis Koo), a top student at the Police Academy, is groomed for a special assignment -- to crack open the Hung Hing triad from the inside as an undercover agent. Shing is able to join up with the Hung Hings and becomes close friends with notorious gangster Fei Ling (Andy Lau). However, when Fei Ling and his henchmen become involved in a gang war with another triad, Shing learns that the rival gang has also been infiltrated by an undercover cop, White Head (Sui-Kei Lee). When Shing is given his assignment to wipe out the enemy gang, he must decide if his loyalty is with the law or with the triad. ~ Mark Deming, Rovi