[25] Immigration in the 19th century was driven by British colonialism—tribal and low castes were brought in from central India to labour in tea gardens and educated Hindu Bengalis from Bengal to fill administrative and professional positions.

[31] Immigration from East Bengal to Assam became cross-border in character following Partition of India—the 1951 census records 274,000 refugees between 1947 and 1951, most of who are estimated to be Hindu Bengalis.

[39] Many of the suspected infiltrators were the illiterate poor and the big landowners, who benefited from the cheap labour they provided, gave them legal aid to defend themselves at the tribunals.

[42] These tribunals were finally shut foen in 1972 on the claim of most infiltrators being caught; and also because after the Indo-Pakistani War of 1971 the adversarial East Pakistan was replaced by Bangladesh, a friendly nation.

[44] The Supreme Court of India repealed it in July 2005 as unconstitutional based on a public interest litigation filled by Sarbananda Sonowal,[45] a former AASU student leader.

[46] In August 1975, the Home Ministry had instructed the state governments to use criminal investigation departments to identify illegal aliens in electoral rolls.

[47] In October 1978 S. L. Shakdhar (the then Chief Election Commissioner) declared foreigners' names were being included in electoral rolls in a large scale[48] and that this was done at the demand of political parties[49]—a claim repeated by a cabinet minister in the Rajya Sabha in November 1978.

[52] When the member of parliament from the Mangaldoi constituency died in March 1979 the Election Commission started the process for a by-election and in April 1979 published the draft electoral rolls and ordered a summary revision.

[54][55] Though the issue of illegal aliens in electoral rolls had been simmering for some years at the national official level, the large numbers at Mangaldoi brought it into sharp public focus and provided the immediate trigger for the Assam Movement—AASU launched its first protest program on 8 June 1979 demanding the "detection, disenfranchisement and deportation" of foreigners.

[56][57] The review process was opposed by political parties, especially the involvement of the police and the executive (and not judicial) officers,[58] and the Chief Election Commissioner, Shakdhar, halted the activity of the tribunals[59]—the final electoral list of Mangaldoi was never released.

[60] Shakdhar, who had earlier warned against foreigners' names in the electoral rolls announced a change his position in September 1979 and pushed the revision to after the 1980 general election polls.

But Indira Gandhi was able to come back to power very soon—in 1978 she split the Congress party to better defend herself and regained membership of the Lok Sabha via a by-election in Chikmagalur, a seat vacated by a party-man; in July 1979 she was able to bring down the Desai government by promising support to Charan Singh, a breakaway leader; a month later she withdrew support to the Charan Singh government necessitating early general elections;[62] and after the general elections in 1980 she became the prime minister once again.

In October 1984 she was assassinated and her son Rajiv Gandhi became the prime minister who, having won a landslide victory in the 1984 Indian general election, settled the Assam Movement and a few other conflicts in a flurry of accords.

[70] The Hazarika government too fell, within ninety four days in December 1979, when the Congress withdrew support and President's Rule was imposed for the first time in the state of Assam.

[71] Since the President's Rule could not be extended beyond a year Congress (I), originally with only 8 members, was able to attract defections from other parties, obtain the support of the CPI, and form a government in December 1980 under the leadership of Anwara Taimur, the only woman or Muslim to have been a chief minister in post-Indian Independence Assam's history.

[76] The election was boycotted by the movement and a number of opposition political parties did not participate; and polling took place amidst extensive inter-ethnic violence.

The movement leadership was augmented by an organisation called All Assam Gana Sangram Parishad (AAGSP) that was constituted in August 1979 by representatives from civic and regional political parties.

She did not accept the demand to use the NRC 1951 and the Census report of 1952 as the basis for identifying foreigners and suggested 24 March 1971 as the cut-off date instead since she wanted to factor in the Liaquat–Nehru Pact of 8 April 1950 and her own agreement with Sheikh Mujibur Rahman in 1972.

[85] The general strike (a 12-hour bandh) on 8 June 1979, sponsored by the AASU, demanding the "detection, disenfranchisement, and deportation" of foreigners could be considered as the beginning of the Assam Movement.

[86] This was followed by the formation of the All Assam Gana Sangram Parishad, an ad hoc coalition of different political and cultural organizations, on 26 August 1979[79][80] At the initial stage the protests were peaceful and the movement enjoyed wide popular support especially among the Assamese people as the Satyagraha program from 12 to 17 November 1979 demonstrated when estimated 700,000 in Guwahati and 2 million in the entire state courted voluntary arrests;[87] but by the end of November, the initial optimism of a negotiated settlement gave way to pessimism.

Khargeswar Talukdar, the 22-year-old general secretary of Barpeta AASU Unit, was beaten to death and thrown into a ditch next to the highway at Bhabanipur.

The Indira Gandhi-led government imposed assembly elections in the state as a challenge to the movement leading to widespread ethnic violence and breakdown of political order.

[97] The two-month old Keshab Gogoi government had fallen and the assembly dissolved on 19 March 1982, and under the then constitutional rules, a fresh election had to be held within a year.

[103] In a conversation with journalist Shekhar Gupta in December 1982 the electoral campaign manager of the Congress (I), Rajesh Pilot, stated that the government intended to hold elections to politically finish the movement leaders.

[104] Even as the AASU-AAGSP leadership was returning to Guwahati on 6 January 1983 from yet another failed talk at New Delhi, the government announced that elections will be held with staggered polling on 14, 17, and 20 February 1983.

[108] The AASU-AAGSP leaders were arrested when they landed at the Guwahati airport,[109] and the Government of Assam imposed censorship on two local newspapers that supported the movement.

[115] The political party leaders made inflammatory speeches during the campaign—the railway minister Ghani Khan Choudhury from Congress appealed to the Bengali Muslim immigrants to retaliate in kind to violence,[118] and Atal Bihari Vajpayee warned of dire consequences if elections were held.

[121][122] On 18 February 1983, during the Nellie massacre, a mob — primarily composed of indigenous Tiwas and semi-indigenous lower caste Hindus — killed thousands of suspected muslim immigrants, in 14 villages in Nagaon district.