In the 30 years between 1960 and 1990, South Africa was subject to a complex and evolving set of sanctions aimed at influencing the South African government to dismantle the apartheid system. In the process, numerous innovative strategies were forged that have been a subsequent inspiration for other solidarity movements in support of oppressed peoples around the world. The resulting diplomatic, cultural and economic isolation confirmed the apartheid government's pariah status.

These international initiatives were not intended to pressure the main parties in South Africa to engage in a process of negotiations but rather aimed to end apartheid. Later the proponents of 'constructive engagement' – and most notably the British government under Margaret Thatcher – were able to draw on their credibility as 'friends' to encourage South African President F.W. De Klerk to engage with the African National Congress (ANC). At the same time, by the late 1980s the Soviet Union and many African governments encouraged the ANC to negotiate a political resolution to the conflict.

In retrospect, it seems that the various punitive measures were only indirectly influential in influencing the government's decision on whether and when to negotiate a transition. Yet while other external and internal factors were decisive, it seems that sanctions had the effect of strengthening the position of those in the white community – and crucially, in the business sector – who recognised the need for reform. They were also likely to have been an important factor in building support for negotiations amongst a white electorate tired of international isolation and being treated as a pariah in the global community. Finally, they were undoubtedly a source of support for the opposition and the ANC continued to value their influence during the negotiations process.

Efforts to isolate apartheid South Africa were initiated on three fronts: individuals and groups leading anti-apartheid campaigns in their own countries; governments acting individually or in concert through organisations such as the Commonwealth; and the UN.

International efforts to abolish the apartheid system of discrimination date from the early 1960s, in response to the ANC's 1958 appeal for international solidarity. In 1962 the UN General Assembly passed a resolution that deemed apartheid to be a violation of South Africa's obligations under the UN Charter and a threat to international peace and security. The resolution paved the way for voluntary boycotts by requesting Member States to break off diplomatic relations and to cease trading with South Africa (arms exports in particular), and to deny passage to South African ships and aircraft. It also established the UN Special Committee against Apartheid, which was to coordinate many of the efforts to impose punitive sanctions in the coming decades. Most Western governments rejected the resolution's call for sanctions and ignored the new committee. Yet the resolution lent moral and political support to the growing civil society-based international solidarity campaign – most notably the London-based Anti-Apartheid Movement – which pressed ahead with calls for economic and other sanctions.

Perhaps most innovative were the efforts to isolate South Africa socially and culturally that were instigated by civil society activists and then incorporated into the policies of sympathetic governments.

An 'academic boycott' was instigated in 1965 by a group of British university staff. It isolated scholars in South Africa by constraining their access to research and their opportunities to publish internationally and engage with counterparts abroad. The boycott was more of an irritation than a true impediment because it was easily circumvented. Furthermore, it was not a strategic lever to influence the government. It was also controversial, with many troubled by its undermining academic freedom and arguing that knowledge should be treated differently from material commodities. Yet supporters, including Archbishop Desmond Tutu, claimed that it triggered awareness in white liberal institutions that they were not exempt from a role in undermining the apartheid system.

Cultural sanctions during the 1980s were endorsed by a UN resolution indicating foreign artists should not work with South Africa. These sanctions were, however, a voluntary code enforced through public pressure and championed by celebrities and some cultural institutions. White South African artists were effectively banned from touring the world and non-South Africans were ostracised for performing in South Africa.

Perhaps the most influential initiative was the 'sports boycott', imposed initially because of the government's rigid adherence to apartheid in sport. Beginning with its 1961 expulsion by FIFA from international football, South Africa was then excluded from the 1964 Tokyo Olympics before being decisively and humiliatingly expelled from the Olympic Games movement in 1970, after almost 50 countries threatened to boycott the games if South Africa was included. It was also selectively banned from much of test match cricket. Campaigners continued to pressure sports bodies to exclude South Africans in tennis and rugby. The high point of protest occurred at the 1981 Springbok tour (rugby) of New Zealand in which thousands protested, invaded pitches and ended the tour. Efforts by campaigners were endorsed by the Commonwealth in 1977 and further codified in the 1985 UN International Convention Against Apartheid in Sports.

Sports are a key interest in much of South Africa's white communities so their exclusion from the international arena was more widely felt than the other academic, cultural and economic sanctions. The initial goal was to de-racialise South African sport but by the early 1980s it was aimed at forcing the government to abandon apartheid. While there is little evidence that it directly contributed to the De Klerk government's decision to negotiate, the sports boycott was perhaps the most obvious sign to the public that the world did not approve of their country's policies.

In addition to trying to isolate South Africa, campaigners sought to hurt its economy. A number of initiatives were tried, from imposing an oil embargo to trade sanctions and finally a series of disinvestment initiatives. The oil embargo was first proposed by the UN in 1963 but made little progress until Arab governments acted to impose an embargo in 1973 – a move that was counteracted when the government successfully obtained assistance from multinational oil companies to continue supply. Despite General Assembly resolutions in 1979 and 1980 and support from many oil-producing countries, including OPEC, opposition from key European and North American governments constrained the comprehensive implementation of that instrument.

The economic sanctions strategy was renewed in the mid-1980s, spurred on by the mass resistance to the attempted reforms introduced in the 1983 constitution and the government's subsequent violent crackdown and imposition of a state of emergency in 1985. The European Community and Commonwealth countries imposed limited trade and financial sanctions. The US administration of President Reagan opposed sanctions but imposed a limited export ban to head off stronger action in the US Congress. This move was trumped, however, when the US legislature forced through the 1986 Comprehensive Anti-Apartheid Act banning new US investment and new bank loans, sales to the police and military, and specific prohibitions against a range of goods – although strategic minerals, diamonds and gold, South Africa's largest export, were not included.

Innovative private sector initiatives complemented these governmental actions. Especially in the US, campaigners lobbied businesses to end their activities and investments with the South African state and businesses. Concerned shareholders introduced resolutions at company AGMs aimed at getting them to adopt the 'Sullivan Principles,' which required that businesses operating in South Africa ensure that all employees were treated equally in an integrated environment, both inside and outside the workplace, as a condition of doing business (which essentially made it impossible to operate given apartheid laws).

Campaigners also lobbied institutional investors, such as pension and endowment funds, to withdraw direct investments from South African-based companies and for US companies to divest from their South African interests. This 'divestment' strategy became a key focus of campaigning at American universities. By 1990 more than 26 US states and 90 cities had taken some form of binding economic action against companies doing business in South Africa. By the late 1980s, most of the world's largest companies had withdrawn from South Africa – motivated by a combination of the reputational risk of continued operations and because the climate for investment in South African had deteriorated badly.

In retrospect, analysts suggest that the direct impact of these economic sanctions was limited. South Africa circumvented trade sanctions through transshipment via countries not participating in the embargoes. The divestment campaigns were costly to the foreign firms that withdrew – often selling assets cheaply to local white businesses but keeping non-equity links that permitted them to continue operating – but did not significantly dent the economy.

Far more painful economically than the trade sanctions was the financial crisis that gripped the country from the mid-1980s, due to the deteriorating investment climate. From 1983 a series of urban uprisings, strikes and consumer boycotts combined with the ANC's strategy of economic warfare, industrial sabotage and attacks on government targets to bring the country to a standstill. The government responded by repealing some apartheid laws and imposing a national state of emergency in 1985. Against this context of increasing ungovernability, many expected the government to announce significant reforms to address the escalating tension. But Botha responded by informing the world that his government would not be susceptible to any pressure – whether from within or from without – and was prepared to go it alone if necessary.

Shortly thereafter, Chase Manhattan Bank declared it would not renew its short-term loans, triggering a liquidity crisis as other lenders similarly withdrew credit. South Africa's economy was highly dependent upon the willingness of foreign lenders to refinance its heavy external debt and these actions precipitated a 50 per cent drop in the currency's value and created severe capital scarcity. This financial crisis was brought on by the decisions of private lenders, who judged that South Africa's faltering economy, market uncertainties and political turmoil combined to make it unattractive for investment. Their motive was to mitigate their own financial risk rather than to trigger changes to apartheid and their decisions to withdraw preceded the imposition of governments' sanction policies. Yet it was the most economically damaging act of external actors.

In the global context of decolonisation and expanding civil rights, apartheid South Africa was an international pariah for decades. Yet Cold War confrontation had combined with South Africa's profitable investment environment to encourage many Western governments to support the NP government as an ally. As the communist governments in Eastern Europe collapsed, this polarisation eased and Western allies began to pressure the government to reform.

Yet several governments refused to participate in imposing sanctions or other punitive behaviour, expressing doubts that they would be economically effective and concern that they would make Afrikaners more intransigent while being most harmful to the economically vulnerable black population. The chief opponents of sanctions were Margaret Thatcher and Ronald Reagan. Analysts debated the effectiveness of their 'constructive engagement' policies. According to Sanford Ungar and Peter Vale:

"Having been offered many carrots by the United States over a period of four-and-a-half years as incentives to institute meaningful reforms, the South African authorities had simply made a carrot stew and eaten it. Under the combined pressures of the seemingly cataclysmic events in South Africa since September 1984 and the dramatic surge of anti-apartheid protest and political activism in the United States, the Reagan Administration was finally embarrassed into brandishing some small sticks as an element of American policy. The Reagan sanctions, however limited, are an important symbol: a demonstration to the ruling white South African nationalists that even an American president whom they had come to regard as their virtual saviour could turn against them."

On the other hand, continued closeness with the Pretoria government may have allowed the UK to influence the South African government's decision to reform. Herman Nickel, US ambassador to South Africa 1982-86, argued that the then British ambassador to South Africa, Sir Robin Renwick, was able to play an important role in encouraging De Klerk to release Mandela and facilitate negotiations precisely because he represented a government that had resisted pressure to impose sanctions. He therefore retained the access and influence that the US lost when Congress overrode Regan's veto on sanctions because, "once Congress had shot its arrow, the American quiver was empty" (New York Times, 15 May 1994).

Despite the array of initiatives designed to pressure or encourage the South African government to abandon apartheid, they were not decisive. Instead, a combination of internal and external factors created conditions that led both the NP and the ANC towards the realisation that their aims might be best met through political negotiations.

The apartheid system was riddled with economic inefficiencies and intrinsically unsustainable. This structural problem was exacerbated by the financial crisis of the 1980s and compounded by the increasingly widespread economic sanctions and embargoes on South African companies and goods – which also had significant symbolic impact. These factors convinced many in South Africa's influential business community that it was necessary to seek a more dramatic solution.

These economic challenges surfaced alongside other geopolitical developments. Key was the collapse of the Soviet Union and the discrediting of communism throughout Eastern Europe and in much of Africa. The ANC had received considerable backing and been associated with advocating state socialism. Apartheid leaders used fear of communism as a central justification for their policies. Thus the collapse of communism helped to increase their confidence when ANC leaders indicated they had relinquished their socialist aspirations. De Klerk later acknowledged that it would not have been possible for him to pursue political negotiations if the 'communist threat' had remained strong. Furthermore, the peace processes in neighbouring states and their rapprochement with the South African government meant the ANC was cut off from some of its previous bases.

Perhaps most significant of all, however, was the strength of the opposition in the democracy movement. As the country became increasingly ungovernable, many NP leaders began to realise that incremental reform would be unlikely to contain the conflict over the longer term. Yet while international isolation and the sanctions regimes may not have decisively forced the government to change its policies, it seems that they were influential in strengthening the case of those who argued for reform. They also offered considerable moral, political and practical support to various elements in South Africa's anti-apartheid democracy movement. Black leaders at the time and subsequently emphasised the effectiveness of the sanctions, and on his release from prison Nelson Mandela argued that lifting sanctions then would have risked aborting the process towards ending apartheid.

Crucially, international sanctions may have also helped to create a climate within South Africa's white communities that was more supportive of reform and endorsed De Klerk's strategy. This support became critical in 1992 when, responding to intense criticism from conservatives, he called a risky referendum to gauge the support of the white electorate. His overwhelming victory confirmed that the majority of whites supported a negotiated settlement. Ultimately, however, it seems that it was the leadership shown by pro-negotiation elements in all the parties that was responsible for South Africa's successful transition.