Since the entire population of Arkham is made up of criminals running wild on the streets, Sharp secretly hopes they will destroy each other inside walled confinement instead of committing crimes in Gotham. This is supported by the TYGER mercenary forces, who enforce this policy through the liberal use of their firearms on any escaping denizens of Arkham City. Once all the criminals are trapped inside the prison city, they are told they may do as they please, but there is only one rule: Do not try escaping or you'll be shot dead.

To guard the perimeter of Arkham City the mayor does away with Arkham Asylum's old security force and replaces them with professional mercenaries from a private military organization, TYGER (who are subjugated to brainwashing by Strange). This will be a city only for villains, and is made up of Gotham City's most notorious slums, including Crime Alley. He then undertakes a bold new project: To move all the former inmates of incarceration at both places into a walled-off urban district, Arkham City. His first act is to announce ruined Arkham Asylum and Blackgate Prison both unfit to house criminals, sane or insane. This is successful, and Sharp is elected mayor of Gotham (though it's actually thanks to Hugo Strange's partnership with Rā's al Ghūl). This is partially to salvage his image, in tatters after the single worst asylum riot took place at a crucial time when Sharp was trying to convince the people of Gotham City to vote for him. The administrator of Arkham, mayoral candidate Quincy Sharp, soon takes advantage of Batman's defeat of the Joker at Arkham and claims the credit himself for bringing the asylum back under control, perhaps saying Batman was working under his orders. Eighteen months after the chaotic events of Batman: Arkham Asylum, both the Elizabeth Arkham Asylum for the Criminally Insane and Blackgate Prison remain gutted, the former in a massive breakout launched by the inmates, lead by the Joker and the latter due to a mysterious fire, which the Joker hints was caused by him for his plans in Arkham Asylum.

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