Short answers, pulled from the story.
The Partition of India took place in August 1947, creating two independent dominions: the Union of India and the Dominion of Pakistan. Pakistan itself later split into two nations: the Islamic Republic of Pakistan and the People's Republic of Bangladesh, following Bangladesh's independence in 1971.
The Partition of India displaced between 12 and 20 million people along religious lines. The 1951 Census of Pakistan identified 7,226,600 displaced persons, while the 1951 Census of India counted 7,295,870. In Punjab alone, total migration is estimated at 12 million people.
Estimates of the death toll from partition violence vary widely. As of 2009, estimates still ranged between two hundred thousand and two million. Most scholars accept approximately one million deaths, with Punjab recording the highest concentration of violence.
The border, known as the Radcliffe Line, was drawn by Sir Cyril Radcliffe, a London barrister who chaired the boundary commissions for both Punjab and Bengal. On every major issue the four judges on each commission divided two and two, leaving Radcliffe to make the final decisions himself.
The Lahore Resolution was passed by the Muslim League at its March 1940 session in Lahore, demanding that Muslim-majority areas in the north-western and eastern zones of India be grouped into independent, sovereign states. It formalized the League's demand for a separate homeland and became the foundational political document of the Pakistan Movement.
Direct Action Day was declared by Muhammad Ali Jinnah for the 16th of August 1946, as a show of Muslim League pressure for a separate Pakistan. In Calcutta that day, communal violence erupted and continued for three days, killing approximately 4,000 people by official accounts. Historians describe the killings as the first communal violence to display elements of ethnic cleansing, with homes entered and destroyed and women and children attacked.