I have a city that has a population of 2.9 million and an urban footprint around 2,037 square kilometres. For reasons unknown, it's been sealed off from the outside world by a shadowy military organization by disabling all internet and cell phone communications, disabling all wireless communications. A large fleet of ships blockades the city's harbour and extends along the surrounding coastline. A strictly enforced no-fly zone stops civilian aircraft flying over the area and a massive wall prevent anyone from entering or exiting the city.
The only problem is that I have no idea how many soldiers this organisation would need to efficiently maintain their occupation and keep the population in line.
How many soldiers would need to be deployed?