Hypothetically, what would it take to takeover Manhattan?

Blow the bridges,cut all communication with the outside world,cut power to all of Manhattan,exploit the reason for doing this(hit all the banks),have an escape rout all laid out and get out asap because SWAT teams by the hundreds will be on you within the hour.If you plan on ripping the banks off you need to already be in place because shutting the power down will make some vaults impossible to get into.You would need several companies of crack troops to blow the bridges,get people out of the way and transfer what ever you are after.They may have to engage the SWAT teams and the law enforcement already on the island so you need several tactical companies with heavy firepower to take out precincts before they can respond.As soon as SWAT starts showing up by chopper and boat there will be total caos and there will be casualties on both sides,i hope the take is enough to pay the surviors that could escape if any do.Your talking about at least 6 companies of combat troops and several people at each bank plus other computer and communication people,there should have been people already in place for weeks or monthes for a job this size.One person said several thousand,its very possible that it would take that many but I think at a minimum one thousand to twelve hundred fifty with at least half being tactical.The whole key will be the response time of SWAT and if the perpetrators have RPGs to deal with airborne SWAT and seaborn SWAT.All of these folks are not going to escape,the escape rout is by sea or air and 1200 some odd criminals are not going to get away clean.Timing is everything and shock and awe is priceless,flash/bangs can freeze a lot of folks,even law enforcement can be caught unprepared and unable to respond automatically.It would take millions to put together an operation like this,so I hope the take is worth it.

To take control of it, several thousand. To hold it - not possible.

A bunch of lawyers and bankers. Been done.

Chase is on the ball. Your thought process is dated.

After the libs take away all of the guns it would take about 250.

-Send a large Contingent of Muppets In ( led by a clever Green Frog ) to surround it, And have Them Stage a big Concert- in Central Park. They'll have the People of Manhattan eating out of Their Paws- without firing a Shot !! :)

Zero, a computer hacker could shut down the city remotely . Military action is really obsolete.