UP, CP People started to come in Pakistan from 1950.

The Partition of India was the partition of the British Indian Empire that led to the creation of the sovereign states of the Dominions of Pakistan and India on 15 August 1947 with the division of the Punjab.

The newly birthed Pakistan faced a number of immigration and naturalization difficulties due to the division of Punjab and Punjabi nation.

The Punjabi Hindus and Punjabi Sikhs were displaced from the western side of Punjab to the eastern side of Punjab and the Punjabi Muslims were displaced from the eastern side of Punjab to the western side of the Punjab.

In the riots which preceded the partition in the Punjab region, about 2 Million people were killed in the retributive genocide and 20 Million people were displaced.

The Time Magazine of September 1947 gave killing static around one million people. However, it was the largest genocide after the Second World War.

UNHCR estimates 14 million Muslim Punjabis, Hindu Punjabis, Sikh Punjabis were displaced during the partition; but, it was the largest mass migration in human history too.

However, after the death of Muhammad Ali Jinnah on 25 December 1948, the problem of religious minorities also flared in Sindh and United Provinces, during 1949 and early 1950.

The Liaquat Ali Khan took the advantage of the situation and started to create the atmosphere and circumstances for the help of Urdu-speaking population of United Provinces and to settle them in the Pakistan.

Liaquat Ali Khan met the Indian Prime Minister Jawaharlal Nehru to sign the Liaquat-Nehru Pact in 1950 to protect the religious minorities on both sides of the border. But, practically, he started to patronize the infiltration of Urdu-speaking communities from the United Provinces of Pakistan.

Therefore, after the Liaquat-Nehru Pact in 1950, the Urdu-speaking communities from the United Provinces, started to infiltrate the Pakistan which polarized the West Pakistani population, especially in the cities of Karachi, Lahore, Rawalpindi, Multan, Hyderabad and other parts of Punjab and Sindh Provinces.

As the result of infiltration of Urdu-speaking communities from the United Provinces of Pakistan, in 1951, close to half of the population of the Lahore, Karachi, Rawalpindi, Multan, Hyderabad and other major cities of Pakistan were Urdu speaking infiltrators from India.