The Radcliffe Line became the international border between India and Pakistan (which also included what is now Bangladesh) during the partition of India. The line divided Bengal into Indian held West Bengal and East Bengal which became East Pakistan.
The line was decided by the Border Commissions headed by Sir Cyril Radcliffe, who was to divide equitably 175,000 square miles (450,000 km2) of territory with 88 million people. The line took effect on 17 August 1947 after the Partition of India.
On 15 July 1947, the Indian Independence Act 1947 of the Parliament of the United Kingdom stipulated that British rule in India would come to an end just one month later, on 15 August 1947. The Act also stipulated the partition of the Provinces of British India into two new sovereign dominions: the Union of India and the Dominion of Pakistan.
The idea behind the Radcliffe Line was to create a boundary which would divide India along religious demographics, under which Muslim majority provinces would become part of the new nation of Pakistan and Hindu and Sikh majority provinces would remain in India. Pakistan was intended to be a homeland for Indian Muslims and India with a Hindu majority was to be a secular nation.
Since the Partition of India was done on the basis of religious demographics, Muslim majority regions in the north of India were to become part of Pakistan. Baluchistan and Sindh (which had a clear Muslim majority) automatically became part of Pakistan.
The challenge however, lay in the two provinces of Punjab (55.7% Muslims) and Bengal (54.4% Muslims) which did not have an overpowering majority. Eventually, the Western part of Punjab became part of West Pakistan and the Eastern part became part of India (Eastern Punjab was later divided into three other Indian states).
The state of Bengal was also partitioned into East Bengal (which became part of Pakistan) and West Bengal, which remained in India. After Independence, the North West Frontier Province (located near Afghanistan) voted with a decision to join Pakistan.
Each boundary commission consisted of 5 people – a chairman (Radcliffe), 2 members nominated by the Indian National Congress and 2 members nominated by the Muslim league. The Bengal Boundary Commission consisted of Justices C. C. Biswas, B. K. Mukherji, Abu Saleh Mohamed Akram and S.A.Rahman. The members of the Punjab Commission were Justices Mehr Chand Mahajan, Teja Singh, Din Mohamed and Muhammad Munir.
Radcliffe arrived in India on 8th July 1947 and was given five weeks to work on the border. Upon meeting with Mountbatten, Radcliffe travelled to Lahore and Kolkata to meet his Boundary Commission members, who were primarily Jawaharlal Nehru representing the Congress and Muhammad Ali Jinnah representing the Muslim League.
On July 8, the British lawyer Sir Cyril Radcliffe arrived in Indian with a brief for a line on the map that would divide Hindu-majority lands from Muslim-majority ones in as equitable a manner as possible. Radcliffe was a brilliant legal mind, but he had no border-making experience, nor had he ever been to India — though such “impartiality” was judged to be an advantage by all parties involved.
Both parties were keen that the boundary be finalised by 15th August 1947, in time for the British to leave India. As requested by both Nehru and Jinnah, Radcliffe completed the boundary line a few days before Independence, but due to some political reasons the Radcilffe Line was only formally revealed on 17th August 1947, two days after Independence.
There were two major disputes regarding the Radcliffe Line, the Chittagong Hill Tracts and the Gurdaspur District. Minor disputes evolved around the districts of Malda, Khulna, and Murshidabad of Bengal and the sub-division of Karimganj of Assam.