Till Indian remember partition of India
With the announcement of partition it became very clear that the country will be parted into two parts and the boundaries will depend on the concentration of Religion in those parts. Hindus and Muslims were both present in almost all parts of the country. Calcutta had a population consisting of 56% Muslims and 40% Hindus. It was clear that if Muslims prove their dominance in that part of the country, it will be theirs. It was a day of widespread riot and manslaughter initiated by the Muslim League, around 5000 people where killed during the riot.
The news went up to the north and the race to prove the dominance started flowing across the country. It was mostly the Northern part which was affected later. Punjab had relatively lesser population of Muslims and was dominated by Sikhs. Similarly, Lahore had a less population of Hindus and Muslims dominated that part. Tens of Thousands of people where killed in those riots. I am not sure if I am right with stats but more than 100,000 people tried to cross the border but due to lack of food and facilities a large proportion of them died. Mothers left their kids and Sons left their old parents in the way. It was very ugly.
It was always clear that if you tell to your country that partition will be done by looking at the concentration of religion such riots would happen.