The division of Punjab was caused much of the sorrow and created these deep seated wounds between Punjabis on both sides of the border. Here is a good analsis of the the Radcliffe Award that divided the two between India and Pakistan:
Source: http://www.unc.edu/depts/diplomat/archives_roll/2002_01-03/chester_partition/chester_partition.html
Analysis of the Boundary Decision
The Facts of the Award
The final boundary, known as the Radcliffe award, allotted some sixty-two percent of the area of undivided Punjab to India, with fifty-five percent of the population.15 The boundary ran from the border of Kashmir State south along the Ujh River, leaving one tehsil16 of Gurdaspur District to Pakistan and allotting the remainder to India. Where the Ujh met the Ravi River, the boundary followed the Ravi southwest, until it met the existing administrative line dividing Amritsar District from Lahore District. Radcliffe was careful to specify that the relevant administrative boundaries, not the course of the Ujh or the Ravi, constituted the new international boundary. The boundary then ran through Lahore District, along tehsil and village boundaries, leaving the district’s easternmost corner in India. When the Radcliffe boundary met the Ferozepore District line, it turned to follow the River Sutlej along the administrative boundary between Ferozepore and Montgomery Districts. The Radcliffe line ended where it met the border of Bahawalpur, a princely state whose ruler, like the Maharajah of Kashmir, had the choice of acceding to Pakistan or India.
The primary feature of this line was that it divided Amritsar, now in India, from Lahore, which went to Pakistan. By and large it followed major administrative divisions, although it did meander between villages in the Kasur region southeast of Lahore. The two most controversial elements of this line involved Gurdaspur and Ferozepore. Pakistani critics interpreted Radcliffe’s decision to grant most of Gurdaspur District to India as an attempt to provide India with a land link to Kashmir. As one element of the beginnings of the Kashmir conflict, this allegation remains controversial. It is worth noting that no all-weather road linked Kashmir and India in 1947; when the first Indo-Pakistani war began in late 1947, India airlifted troops and supplies into Kashmir rather than take an overland route. The other controversy was over Ferozepore’s allocation to India; this decision came as a surprise in the wake of early August leaks indicating that Radcliffe would allocate a section of Ferozepore to Pakistan.
In accordance with Mountbatten, Nehru, and Jinnah’s demands that he complete his work before August 15, Radcliffe submitted his award on August 12. By this time, Mountbatten had changed his mind (for reasons discussed below) and asked Radcliffe to delay the award until after August 15. Radcliffe refused, but Mountbatten had his way, choosing not to release the award until August 16, when he discussed it with the Indian and Pakistani leaders at a meeting in New Delhi. On August 17, the award was finally published.
