UP, CP People started to come to Pakistan since 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 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 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 within a short span of time.

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 of India, during 1949.

The Liaquat Ali Khan took advantage of the situation and started to create the atmosphere and circumstances to help the Urdu Speaking population of the United Provinces of India and to settle them in 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, in particular, he started to patronize the infiltration of Urdu Speaking communities from the United Provinces of India to Pakistan on a mass scale.

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

In a matter of fact, the Liaquat-Nehru pact was for the settlement of dislocated Punjabis due to the division of Punjab and not for the people of other areas. Punjab was declared as an agreed area and other areas were declared as Non-Agreed areas for migration, but as a Prime Minister of Pakistan, Liaquat Ali Khan manipulated the agreement to settle the people of his native province in Lahore, Rawalpindi, Multan, Hyderabad and other parts of the Punjab and Sindh Provinces at large scale, especially in Karachi to control the capital and port city of Pakistan.

In 1947, only the UP, CP politicians, bureaucracy and the establishment came in Karachi, the capital of Pakistan, to take the charge of Pakistan. In 1948, the students of Darul Uloom Nadwatul Ulama, Darul Uloom Deoband, and Barelvi institutions in the United Province of India and the Students of Aligarh Muslim University, with their families were brought into Pakistan through special trains by declaring them the Potential Immigrants from India. They were provided the services in teaching institutions and government departments of Pakistan. Students of Aligarh Muslim University were taken as the high-rank officers in the bureaucracy and the establishment of Pakistan. In Karachi, the capital of Pakistan, to settle them, the first residential colony for them with the name of the PIB Colony was built by the Chief Minister of Sindh, Pir Illahi Bux (3 May 1948 to 4 February 1949).

In Sept 1948, first one Quota System for Pakistan was introduced by the Prime Minister Liaquat Ali Khan and it used a Regional/Provincial model for recruitment in Government Jobs and accordingly; Bengal 42%, Punjab 23%, Potential Immigrants from India 15%, and Karachi had a 2% separate Quota. Other provinces [Sindh, Balochistan and NWFP] and the Princely States had a 17% Quota. Later in Nov 49, instead of using the term Potential immigrants from India, merit was used and the new quota was; Merit 20%, Karachi 2%, Bengal 40%, Punjab including Bahawalpur 23%. All other [Sindh, Balochistan, and NWFP] had a 15% Quota.

Three full provinces Sindh, Balochistan, and NWFP were given 15% Quota and Urdu Speaking Hindustani Muhajir's alone were given 20% in the name of "Merit " and 2% for Karachi alone, that makes it 22%. Ironically, the 15% Quota of Sindh and 23% Quota of Punjab including Bahawalpur, that too normally went to Urdu Speaking Hindustani Muhajir, due to their settlement in the cities and towns of rural Sindh and the urban areas of Punjab from 1950.

As a result of the infiltration of Urdu-speaking communities from the United Provinces of India to 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.