Sean Gilman’s review published on Letterboxd :
A major Johnnie To film, perhaps his most epic in scope. Makes the third part of two trilogies: on modern HK criminal gangs and their relations with the PRC with the Election movies, and on the teamwork and professionalism of cops with Expect the Unexpected and PTU.
Also, it is To's Tarantino film: structured as a series of conversations, with one of the parties pretending to be someone else, with a build-up and diffusion of tension until a final burst of ultra-violence. The difference is To's characters are all business: there's no small talk, no cultural referencing, no background information. Psychology is revealed through work, not chatter.