It was anarchy in Gotham. That, in itself was unsurprising, given the events of the past few years. Truthfully, the complete loss of control started off not as some twisted revolution as expected of Gotham City, but as an act of war in it's finest.
To understand this, you must know that Gotham City is not your average city. Sure, like all other cities there are crime, and criminals, and corruption.
The only difference were that they were not the defining characteristics of the other cities. But in Gotham, crime is. The city, the civilians, the police force, the rich or the poor or the criminals or the socialites- the breath in the stench of crime, day after day, night after night, until the special brand of sanity that Gotham imprints into the very makings of her people.
Well, the beginning of the forced downfall of Gotham was an individual attack of the city issued by a branch of very, very powerful people.
No one knew why they picked out Gotham, out of all the other major metropolis's in the world, to launch their attack upon.
They organization, dubbed by the internet and media as 'Select Few,' is an international organization obsessed with the 'cleansing' of humanity. They believe that, due to the crime and corruption of the modern life, all of humanity apart from a select few who may join them must be eradicated from the surface of the earth.
The other cities and governments, threatened by the sheer power these people hold, elected to form a treaty, a treaty signed by every country and major metropolis. Except for Gotham City, still grieving over the death of Harvey Dent.
Gotham ended up being chosen as the 'world's noble sacrifice.' Many opposed, no doubt, standing their moral grounds and signing petitions and writing letters to the editor. But the threat of them being killed overrules the impending death of the citizens of Gotham. The other cities are too blind to see that once Gotham is gone, Select Few would begin targeting them, unless they offer up another, and another, until their goal is reached while no resistance is met.