The history of Sri Lanka from 1948 to the present is marked by the independence of the country through to Dominion and becoming a Republic. 
Overview.
Periodization of Sri Lanka history:
Dominion (1948–1972).
Dominion status followed on 4 February 1948 with military treaties with Britain, as the upper ranks of the armed forces were initially British, and British air and sea bases remained intact. This was later raised to independence itself and Senanayake became the first Prime Minister of Sri Lanka. In 1949, with the concurrence of the leaders of the Ceylon Tamils, the UNP government disenfranchised the Indian Tamil plantation workers. This was the price that Senanayake had to pay to obtain the support of the Kandyan Sinhalese, who felt threatened by the demographics of the tea estates where the inclusion of the "Indian Tamils" would have meant electoral defeat for the Kandyan leaders. Senanayake died in 1952 after falling from a horse and was succeeded by his son Dudley Senanayake, the then minister of Agriculture. In 1953 he resigned following a massive "Hartal" ("general strike") by the Left parties against the UNP. He was followed by John Kotelawala, a senior politician and an uncle of Dudley Senanayake. Kotelawala did not have the enormous personal prestige or the adroit political acumen of D. S. Senanayake. He brought to the fore the issue of national languages that D. S. Senanayake had adroitly kept on the back burner, antagonising the Tamils and the Sinhalese by stating conflicting policies with regard to the status of Sinhala and Tamil as official languages. He also antagonized the Buddhist lobby by attacking politically active Buddhist Monks who were Bandaranaike's supporters.
In 1956, Sinhala was established as the official language, with Tamil as a second language. Appeals to the Judicial Committee of the Privy Council in London were abolished and plantations were nationalised to fulfil the election pledges of the Marxist program and to "prevent the ongoing dis-investment by the owning companies".
In 1956, the Sinhala Only Act came into being. This established Sinhala as the first and preferred language in commerce and education. 
The Act took effect immediately. As a consequence vast numbers of people mostly Burghers left the country to live abroad as they rightfully felt discriminated against.
In 1958, the first major riots between Sinhalese and Tamils flared up in Colombo as a direct result of the government's language policy.
The leftist Sinhalese Janatha Vimukthi Peramuna drew worldwide attention when it launched an insurrection against the Bandaranayake government in April 1971. Although the insurgents were young, poorly armed, and inadequately trained, they succeeded in seizing and holding major areas in Southern and Central provinces before they were defeated by the security forces. Their attempt to seize power created a major crisis for the government and forced a fundamental reassessment of the nation's security needs.
The movement was started in the late 1960s by Rohana Wijeweera, the son of a businessman from the seaport of Tangalla, Hambantota District. An excellent student, Wijeweera had been forced to give up his studies for financial reasons. Through friends of his father, a member of the Ceylon Communist Party, Wijeweera successfully applied for a scholarship in the Soviet Union, and in 1960 at the age of seventeen, he went to Moscow to study medicine at Patrice Lumumba University.
While in Moscow, he studied Marxist ideology but, because of his openly expressed sympathies for Maoist revolutionary theory, he was denied a visa to return to the Soviet Union after a brief trip home in 1964. Over the next several years, he participated in the pro-Beijing branch of the Ceylon Communist Party, but he was increasingly at odds with party leaders and impatient with its lack of revolutionary purpose. His success in working with youth groups and his popularity as a public speaker led him to organize his own movement in 1967. Initially identified simply as the New Left, this group drew on students and unemployed youths from rural areas, most of them in the sixteen-to-twenty-five-age-group. Many of these new recruits were members of minority so-called 'lower' castes (Karava and Durava) who felt that their economic interests had been neglected by the nation's leftist coalitions. The standard program of indoctrination, the so-called Five Lectures, included discussions of Indian imperialism, the growing economic crisis, the failure of the island's communist and socialist parties, and the need for a sudden, violent seizure of power.
Between 1967 and 1970, the group expanded rapidly, gaining control of the student socialist movement at a number of major university campuses and winning recruits and sympathizers within the armed forces. Some of these latter supporters actually provided sketches of police stations, airports, and military facilities that were important to the initial success of the revolt. In order to draw the newer members more tightly into the organization and to prepare them for a coming confrontation, Wijeweera opened "education camps" in several remote areas along the south and southwestern coasts. These camps provided training in Marxism–Leninism and in basic military skills.
While developing secret cells and regional commands, Wijeweera's group also began to take a more public role during the elections of 1970. His cadres campaigned openly for the United Front of Sirimavo R. D. Bandaranaike, but at the same time, they distributed posters and pamphlets promising violent rebellion if Bandaranaike did not address the interests of the proletariat. In a manifesto issued during this period, the group used the name Janatha Vimukthi Peramuna for the first time. Because of the subversive tone of these publications, the United National Party government had Wijeweera detained during the elections, but the victorious Bandaranaike ordered his release in July 1970. In the politically tolerant atmosphere of the next few months, as the new government attempted to win over a wide variety of unorthodox leftist groups, the JVP intensified both the public campaign and the private preparations for a revolt. Although their group was relatively small, the members hoped to immobilize the government by selective kidnapping and sudden, simultaneous strikes against the security forces throughout the island. Some of the necessary weapons had been bought with funds supplied by the members. For the most part, however, they relied on raids against police stations and army camps to secure weapons, and they manufactured their own bombs.
The discovery of several JVP bomb factories gave the government its first evidence that the group's public threats were to be taken seriously. In March 1971, after an accidental explosion in one of these factories, the police found fifty-eight bombs in a hut in Nelundeniya, Kegalla District. Shortly afterwards, Wijeweera was arrested and sent to Jaffna Prison, where he remained throughout the revolt. In response to his arrest and the growing pressure of police investigations, other JVP leaders decided to act immediately, and they agreed to begin the uprising at 11:00 P.M. on 5 April.
The planning for the countrywide insurrection was hasty and poorly coordinated; some of the district leaders were not informed until the morning of the uprising. After one premature attack, security forces throughout the island were put on alert and a number of JVP leaders went into hiding without bothering to inform their subordinates of the changed circumstances. In spite of this confusion, rebel groups armed with shotguns, bombs, and Molotov cocktails launched simultaneous attacks against seventy-four police stations around the island and cut power to major urban areas. The attacks were most successful in the south. By 10 April, the rebels had taken control of Matara District and the city of Ambalangoda in Galle District and came close to capturing the remaining areas of Southern Province.
The new government was ill-prepared for the crisis that confronted it. Although there had been some warning that an attack was imminent, Bandaranaike was caught off guard by the scale of the uprising and was forced to call on India to provide basic security functions. Indian frigates patrolled the coast and Indian troops guarded Bandaranaike International Airport at Katunayaka while Indian Air Force helicopters assisted the counteroffensive. Sri Lanka's all-volunteer army had no combat experience since World War II and no training in counterinsurgency warfare. Although the police were able to defend some areas unassisted, in many places the government deployed personnel from all three services in a ground force capacity. Royal Ceylon Air Force helicopters delivered relief supplies to beleaguered police stations while combined service patrols drove the insurgents out of urban areas and into the countryside.
After two weeks of fighting, the government regained control of all but a few remote areas. In both human and political terms, the cost of the victory was high: an estimated 10,000 insurgents- -many of them in their teens—died in the conflict, and the army was widely perceived to have used excessive force. In order to win over an alienated population and to prevent a prolonged conflict, Bandaranaike offered amnesties in May and June 1971, and only the top leaders were actually imprisoned. Wijeweera, who was already in detention at the time of the uprising, was given a twenty-year sentence and the JVP was proscribed.
Under the six years of emergency rule that followed the uprising, the JVP remained dormant. After the victory of the United National Party in the 1977 elections, however, the new government attempted to broaden its mandate with a period of political tolerance. Wijeweera was freed, the ban was lifted, and the JVP entered the arena of legal political competition. As a candidate in the 1982 presidential elections, Wijeweera finished fourth, with more than 250,000 votes (as compared with Jayewardene's 3.2 million). During this period, and especially as the Tamil conflict to the north became more intense, there was a marked shift in the ideology and goals of the JVP. Initially Marxist in orientation, and claiming to represent the oppressed of both the Tamil and Sinhalese communities, the group emerged increasingly as a Sinhalese nationalist organization opposing any compromise with the Tamil insurgency. This new orientation became explicit in the anti-Tamil riots of July 1983. Because of its role in inciting violence, the JVP was once again banned and its leadership went underground.
The group's activities intensified in the second half of 1987 in the wake of the Indo-Sri Lankan Accord. The prospect of Tamil autonomy in the north together with the presence of Indian troops stirred up a wave of Sinhalese nationalism and sudden growth of anti-government violence. During 1987 a new group emerged that was an offshoot of the JVP—the Patriotic Liberation Organization (Deshapremi Janatha Viyaparaya—DJV). The DJV claimed responsibility for the August 1987 assassination attempts against the president and prime minister. In addition, the group launched a campaign of intimidation against the ruling party, killing more than seventy members of Parliament between July and November.
Along with the group's renewed violence came a renewed fear of infiltration of the armed forces. Following the successful raid of the Pallekelle army camp in May 1987, the government conducted an investigation that resulted in the discharge of thirty-seven soldiers suspected of having links with the JVP. In order to prevent a repetition of the 1971 uprising, the government considered lifting the ban on the JVP in early 1988 and permitting the group to participate again in the political arena. With Wijeweera still underground, however, the JVP had no clear leadership at the time, and it was uncertain whether it had the cohesion to mount any coordinated offensive, either military or political, against the government.
Republic (1972–2009).
Under Bandaranaike, the country became a republic, the Free Sovereign and Independent Republic of Sri Lanka, the Senate was abolished and Sinhala was established as the official language (with Tamil as a second language). Full independence came as the last remaining constitutional ties with the United Kingdom were broken (e.g., the right of appeal to the United Kingdom's Judicial Committee of the Privy Council ceased, thus establishing the Supreme Court as the country's ultimate court of appeal). Colonial plantations were nationalised to fulfil the election pledges of the Marxist program and to "prevent the ongoing dis-investment by the owning companies".
The Socialist Republic of Sri Lanka is established on 22 May 1972. By 1977, the voters were tired of Bandaranaike's socialist policies and elections returned the UNP to power under Junius Jayewardene, on a manifesto pledging a market economy and "a free ration of 8 seers (kilograms) of cereals". The SLFP and the left-wing parties were virtually wiped out in Parliament, although they garnered 40% of the