India, Oct. 11 -- In the days before Saturday's protest, Delhi Police collected the home addresses, mobile numbers and social media accounts of the people organising it, tracked their movements and checked hotel registers across the city, according to officers who asked not to be named.

On Saturday, police detained political leaders, key organisers of the Cockroach Janta Party (CJP), members of organisations backing the protest and even journalists at Delhi airport, at hotels and guest houses, and at their homes.

The entire strategy, from the deployment of security personnel to the surveillance of organisers and the creation of temporary detention centres in stadiums, community centres and police stations across the city, was drawn up b...