The Milieu Trilogy in order

A set of three influential 1970s Italian poliziotteschi (crime) films directed by Fernando Di Leo: Caliber 9 (1972), The Italian Connection (1972), and The Boss (1973). Known for gritty violence and tales of mafia corruption, these films are considered masterpieces of the genre, often exploring themes of organized crime in Milan. 3 films, 5h 7m in all, in release order.

1. 1
   

   Caliber 9

   1972 · 102 min

   Just out of prison, ex-con Ugo Piazza meets his former employer, a psychopathic gangster Rocco who enjoys sick violence and torture. Both the gangsters and the police believe Ugo has hidden $300,000 that should have gone to an American drug syndicate boss.

   Worth the Hype
2. 2
   

   The Italian Connection

   1972 · 96 min

   When a shipment of heroin disappears between Italy and New York, a small-time pimp in Milan is framed for the theft. Two professional hitmen are dispatched from New York to find him, but the real thieves want to get rid of him before the New York killers get to him to eliminate any chance of them finding out he's the wrong man.

   Worth the Hype
3. 3
   

   The Boss

   1973 · 109 min

   A hitman finds himself embroiled in the middle of a Mafia war between the Sicilians and the Calabrians.

   Popcorn Flick