Full control of the entire territory was not achieved until the beginning of the 20th century, when agreements with other European powers during the Scramble for Africa fixed the colony's interior borders.

Kings such as João I and Afonso I studied Christianity and learned Portuguese, in turn Christianising their nation and sharing the benefits from the slave trade.

In 1884, the United Kingdom, which up to that time refused to acknowledge that Portugal possessed territorial rights north of Ambriz, concluded a treaty recognising Portuguese sovereignty over both banks of the lower Congo.

In the late 1950s the National Front for the Liberation of Angola (FNLA) and the People's Movement for the Liberation of Angola (MPLA) began to organize strategies and action plans to fight Portuguese rule and the remunerated system which affected many of the native African people from the countryside, who were relocated from their homes and made to perform compulsory work, almost always unskilled hard labour, in an environment of economic boom.

Organised guerrilla warfare began in 1961, the same year that a law was passed to improve the working conditions of the largely unskilled native workforce, which was demanding more rights.

In 1961, the Portuguese Government indeed abolished a number of basic legal provisions which discriminated against black people, like the Estatuto do Indigenato (Decree-Law 43: 893 of 6 September 1961).

After these events the Portuguese Government, under the dictatorial Estado Novo regime of António de Oliveira Salazar and later Marcelo Caetano, sent thousands of troops from Europe to perform counterterrorism and counterinsurgency operations.

[citation needed] In 1971, the Portuguese Armed Forces started a successful counter-insurgency military campaign that expelled the three guerrilla movements operating in the East to beyond the frontiers of Angola, the Frente Leste.

The last guerrillas lost hundreds of soldiers and left tons of equipment behind, disbanding chaotically to neighbouring countries or, in some cases, joining or surrendering to the Portuguese.

51 new schools were operating and 82 were being constructed[12][13] By 1972, after the Frente Leste, complemented by a pragmatic hearts and minds policy, the military conflict in Angola was effectively won for the Portuguese.

It changed Angola's status from an overseas province to an autonomous state with authority over some internal affairs, while Portugal was to retain responsibility for defense and foreign relations.

The war was becoming even more unpopular in Portuguese society due to its length and costs, the worsening of diplomatic relations with other United Nations members, and the role it played as a factor in the perpetuation of the Estado Novo regime.

In May of that year, the Junta de Salvação Nacional (the new revolutionary government of Portugal) proclaimed a truce with the pro-independence African guerrillas in an effort to promote peace talks and independence.

[16] The military-led coup returned democracy to Portugal, ending the unpopular Colonial War where hundreds of thousands of Portuguese soldiers had been conscripted into military service, and replacing the authoritarian Estado Novo (New State) regime and its secret police which repressed elemental civil liberties and political freedoms.

[18][19] These events prompted a mass exodus of Portuguese citizens, overwhelmingly white but some mestiço (mixed race) or black, from Portugal's African territories, creating hundreds of thousands destitute refugees — the retornados.

[citation needed] In 1972, the Portuguese National Assembly changed Angola's status from an overseas province to an autonomous state with authority over some internal affairs; Portugal was to retain responsibility for defense and foreign relations.

From the coastal plain, ranging in width from 25 kilometres in the south to 100–200 kilometers in the north, the land rises in stages towards the high inland plateau covering almost two-thirds of the country, with an average altitude of between 1,200 and 1,600 metres.

[citation needed] The Portuguese authorities established several national parks and natural reserves across the territory: Bicauri, Cameia, Cangandala, Iona, Mupa, Namibe and Quiçama.

On the eve of the end of the colonial period, the ethnic European residents numbered 400,000 (1974) (excluding enlisted and commissioned soldiers from the mainland) and the mixed race population was at around 100,000 (many were Cape Verdian migrants working in the territory).

Most of the other large cities in Angola had around the same ratio of Europeans at the time, with the exception of Sá da Bandeira (Lubango), Moçâmedes (Namibe) and Porto Alexandre (Tombua) in the south where the white population was more established.

The two colonies had initially been contiguous, but later became geographically separated by a narrow corridor of land, which Portugal ceded to Belgium, allowing the Belgian Congo access to the Atlantic Ocean.

By 1850, Luanda was one of the most developed cities outside Mainland Portugal in the Portuguese Empire: it was full of trading companies, exporting (together with Benguela) palm and peanut oil, wax, copal, timber, ivory, cotton, coffee, and cocoa, among many other products.

Diamang had exclusive mining and labor rights in a huge concession in Angola and used this monopoly to become the colony's largest commercial operator and also its leading revenue generator.

The American sociologist Edward Ross visited rural Angola in 1924 on behalf of the Temporary Slavery Commission of the League of Nations and wrote a scathing report describing the labor system as "virtually state serfdom", that did not allow Africans time to produce their own food.

The construction of the mine installations and a 300 km railway were commissioned to Krupp of Germany and the modern harbour terminal to SETH, a Portuguese company owned by Højgaard & Schultz of Denmark.

In the north, cassava, coffee, and cotton were grown; in the central highlands, maize was cultivated; and in the south, where rainfall is lowest, cattle herding was prevalent.

The commercial farmers were dominant in marketing these crops, however, and enjoyed substantial support from the overseas province's Portuguese government in the form of technical assistance, irrigation facilities, and financial credit.

Starting in the early 1950s, the access to basic, secondary and technical education was expanded and its availability was being increasingly opened to both the African indigenes and the ethnic Portuguese of the territories.

Education beyond the primary level became available to an increasing number of black Africans since the 1950s, and the proportion of the age group that went on to secondary school in the early 1970s was an all-time record high enrollment.

From the 1920s onward, city and town expansion and modernization included the construction of several sports facilities for football, rink hockey, basketball, volleyball, handball, athletics, gymnastics and swimming.