The North Side Gang, also known as the North Side Mob, was the dominant Irish-American criminal organization (although a large number of Polish-Americans were members as well) within Chicago during the Prohibition era from the early-to-late 1920s and principal rival of the Johnny Torrio–Al Capone organization, later known as the Chicago Outfit.
John Torrio (January 20, 1882 – April 16, 1957) also known as "Papa Johnny", "The Fox", and "The Immune", was an Italian-American mobster who helped build a criminal empire, the Chicago Outfit, in the 1920s; it was later inherited by his protégé, Al Capone.
 He also put forth the idea of the National Crime Syndicate in the 1930s and later became an unofficial adviser to the Genovese crime family.
Ralph "Bottles" Capone, Sr., (January 12, 1894 – November 22, 1974) was a Chicago mobster and an older brother of Al Capone and Frank Capone.
 Ralph Capone got the nickname "Bottles" not from involvement in the Capone bootlegging empire, but from his running the legitimate non-alcoholic beverage and bottling operations in Chicago.
 Further family lore suggests that the nickname was specifically tied to his lobbying the Illinois Legislature to put into law that milk bottling companies had to stamp the date that the milk was bottled on the bottle.
 He was most famous for being named by the Chicago Crime Commission "Public Enemy Number Three" when his brother Al was "Public Enemy Number One".
Henry Earl J. Wojciechowski, also known as Hymie Weiss (January 25, 1898 – October 11, 1926), was an American mob boss who became a leader of the Prohibition-era North Side Gang and a bitter rival of Al Capone.
 He was known as 'the only man Al Capone feared'.
Paul Kelly (born Paolo Antonio Vaccarelli; December 23, 1876 – April 3, 1936) was an Italian immigrant who founded the Five Points Gang in New York City after starting some brothels with prize money earned in boxing.
 It was one of the last dominant street gangs in New York history; Kelly recruited young men who later became prominent criminals of the early 20th century, including Johnny Torrio, Al Capone, Lucky Luciano, Meyer Lansky, Bugsy Siegel and Frankie Yale.
 Kelly was said to support election of Democratic Tammany Hall politicians with his gang's activities at elections.
Black Hand extortion was a criminal tactic used by gangsters based in major cities, in the United States.
 In Chicago Black Hand extortion began around 1900 and had all but faded away by 1920, and the "Mafia" replaced it.
 The Mafia was initially organized by Johnny Torrio, and somewhat organized by Al Capone.
Vincent Drucci, also known as "The Schemer" (born Vincenzo D'Ambrosio; 1898 – April 4, 1927), was an Sicilian-American mobster during Chicago's Prohibition era who was a member of the North Side Gang, Al Capone's best known rivals.
 A friend of Dean O'Banion, Drucci succeeded him by becoming co-leader.
 He is the only US organized crime boss to have been killed by a policeman.
Vincenzo Colosimo (February 16, 1878 – May 11, 1920), known as James "Big Jim" Colosimo or as "Diamond Jim", was an Italian-American Mafia crime boss who emigrated from Calabria, Italy in 1895, and built a criminal empire in Chicago based on prostitution, gambling, and racketeering.
 He gained power through petty crime and by heading a chain of brothels.
 From about 1902 until his murder in 1920, he led a gang that became known after his death as the Chicago Outfit.
 Johnny Torrio was an enforcer whom Colosimo imported in 1909 from New York and who seized control after his death.
 Al Capone, a Torrio henchman, allegedly was directly involved in the murder.
Charles Dean O'Banion (July 8, 1892 – November 10, 1924) was an American mobster who was the main rival of Johnny Torrio and Al Capone during the brutal Chicago bootlegging wars of the 1920s.
 The newspapers of his day made him better known as Dion O'Banion, although he never went by that first name.
 He led the North Side Gang until 1924, when he was murdered, reportedly by Frankie Yale, John Scalise and Albert Anselmi.
Peter Gusenberg a.k.a. ""Goosey"" (September 22, 1888 – February 14, 1929) and his brother Frank were German-American contract killers and members of Chicago's North Side Gang, the main rival to the Chicago Outfit.
 Peter Gusenberg participated in an infamous attack on Al Capone during a vicious gang war.

Question: Who was the friend the main rival of Johnny Torrio and Al Capone during the brutal Chicago bootlegging wars of the 1920s, also known as "The Schemer"?
Answer: Vincent Drucci