In the movie, the Gangster Squad is assembled to go after
Mickey Cohen. However, in real life Chief
W.H. Parker set up the squad to prevent other gangsters from taking over Cohen's rackets after Cohen went to prison on income tax evasion. Whenever the squad learned that out-of-town gangsters were coming to Los Angeles to try to set up new operations, the Gangster Squad would kidnap them, beat them up (some rumors say torture) and then send them back to wherever they came from with the warning that if they ever returned, they would be killed.
