- "There is a war coming, a terrible war. Falcone is losing his grip and his rivals are hungry. There will be chaos, rivers of blood in the street."
- —Oswald Cobblepot to Jim Gordon[src]
While Sal Maroni, Tommy Bones and some of his mobsters were at Lidia's, the hitman Connor (hired by The Penguin) arrived and told Maroni that he had been sent by Falcone before attempting to kill him, but Penguin had secretly set Connor up. The guns that had been hidden for Connor and his cohorts were sabotaged and Maroni's men shot the hitmen dead. Maroni believed that Carmine Falcone was the one who had hired Connor and consequently declared war on his rival.
Maroni and his underlings destroyed many of Falcone's businesses around the town, significantly weakening the mob boss. Maroni himself went to some of the business and shot dead many of Falcone's underlings with a sawed-off shotgun.
Attack on Falcone
While he was checking his prized chickens, Falcone was wounded by a missile fired by two assassins, and was taken to a hospital. It was later revealed that Gotham's City Hall gave Maroni the go-ahead to kill and replace Falcone. Jim Gordon found this unacceptable, as Maroni was a young "hot head" and he believed that he would do more harm than Falcone ever had. The Penguin and Butch Gilzean then invaded Falcone's room and attempted to assassinate him, but are stopped by Jim Gordon. Tommy Bones and some of Maroni's thugs then arrive at the hospital to end the don's life, but a shootout ensues and results in several of the assailants being killed by Gordon and Falcone, Penguin and Butch transported by Gordon and Harvey Bullock to a warehouse owned by Falcone.
After they enter the warehouse, Fish Mooney's gang soon enters, trapping them and calling Maroni. After a conversation where Maroni offends Fish, Fish shoots Maroni dead and a shootout between Fish's gang and Maroni's thugs ensues. Fish's gang wins, trapping Gordon and his affiliates again. But Penguin arrives with a deadly machine gun and massacres all of Fish's gang except for Fish herself, killing the last thug with a pistol. Penguin then pursues Fish on the rooftop, eventually pushing her into the sea after a brief fight, killing her and ending the war. He then triumphantly proclaims himself "King of Gotham."
Penguin becomes the ruler of Gotham City's criminal underworld, and takes over Falcone and Maroni's territories, the former of whom retires from the criminal life and leaves the city.