On 16th August 1946, Jinnah's communal party carried out a pre-planned massacre with the hopes of changing the demographics of Calcutta permanently.
The ulterior motive was to make Calcutta a part of East Pakistan.
With the active support of the then Chief Minister Huseyn Shaheed Suhrawardy, mobs unleashed unprecedented violence.
Estimates put the death toll at anywhere between 5000-10000. This is besides multiple cases of r*pes, loot, and targeted destruction of properties.
When the opportunity presented itself to either fight or perish, the lionhearted Gopal Chandra Mukherjee (also called Gopal Patha) rose to the occasion.
With the support of the Bengali and non-Bengali Hindus, he put up a mighty resistance against the marauding mobs.
By the 4th day, the tables had turned. The motive to change demographics had failed.
It is men like Gopal Chandra Mukherjee who ensured Calcutta remained a part of India (after a year).