The PTU Collection

The real PTU (Police Tactical Unit) are a special unit within the Hong Kong Police Force that perform a number of roles, such as patrolling streets, providing backup to other divisions when needed, aiding disaster response teams, and participating in riot control, among other things. This PTU do all of that, too, but they're fictionalised. Their methods aren't always legal, but they cover their asses well, looking out for each other by stalling for time and hiding truths, except when there's a personal rivalry taking precedence.
The original film was by Hong Kong filmmaker Johnnie To (aka To Kei-Fung) in 2003 and remains to this day one of his best works. The five subsequent TV Movies used some of the same actors but as different characters.

The Original Film:
01. PTU: Police Tactical Unit (2003) Dir. Johnnie To

The Tactical Unit TV Movies:
01. Tactical Unit: The Code (2008) Dir. Wing-cheong Law
02. Tactical Unit: No Way Out (2009) Dir. Lawrence Ah Mon
03. Tactical Unit: Human Nature (2009) Dir. Andy Ng
04. Tactical Unit: Comrades in Arms (2009) Dir. Wing-cheong Law
05. Tactical Unit: Partners (2009) Dir. Lawrence Ah Mon