A year before his election as US president in 1968, Richard Nixon wrote in Foreign Affairs that ``we simply cannot afford to leave China forever outside the family of nations''. It was an assessment that would have monumental consequences.
Mr Nixon's recognition of the geopolitical importance of China was spurred, among other things, by deepening enmity within the communist world between Moscow and Beijing in the late 1960s, America's ensnarement in the Vietnam war, and a growing awareness by America and the USSR that unchecked Cold War nuclear rivalry could generate mutual destruction.
Once elected, President Nixon looked forward to what he called ``an era of negotiations'' with the Soviet Union. For its part, Moscow had quite distinctive reasons for seeking a more co-operative relationship with Nixon's America.
By the late 1960s, the Soviet Union believed it could negotiate from a position of relative strength with the US.
While the Soviet leadership remained anxious about the China following a brief border war between the two states in 1969, it had finally succeeded, at some considerable cost to its economy, in achieving rough nuclear parity in strategic weapons with the US, and believed that American ``imperialism'' had experienced a set-back of global proportions in Vietnam.
Taken together, these factors contributed to a period of improved relations during the Cold War between the United States and the Soviet Union known as detente, a French word denoting the relaxation of tension.
The detente era lasted from 1969 until 1979. It encompassed 60 or so superpower agreements covering a wide variety of issues. Major achievements included normalisation of the political division of Europe through the establishment of diplomatic relations between the states of East and West Germany in 1972 and the signing of the Helsinki Final Act in 1975, which, among other things, recognised a Soviet sphere of influence in East Europe.
In addition, detente made progress in regulating Soviet-American nuclear arms competition. In 1972, the two superpowers signed an arms control measure known as Strategic Arms Limitation Talks (Salt 1).
However, detente did not end the Cold War, and by 1973, particularly after the Yom Kippur war, it was clear that the impulse to compete was steadily overwhelming the desire to co-operate in superpower relations.
Moscow viewed detente as a formal American recognition that the Soviet Union had become an equal superpower, and believed this afforded new opportunities for the Soviet Union to project power globally.
In contrast, Washington saw detente as a new way of containing Soviet military might. By signing diplomatic, strategic and economic agreements with Moscow, the Nixon and Ford administrations expected the USSR would obtain a stake in the international status quo.
These differences in conception almost inevitably led to differences in substantive policy.
The defeat of US-backed South Vietnam in 1975, and the unification of Vietnam on a communist basis, helped embolden the Soviet Union to engage in a series of military interventions in the Third World, to support allies in places like Angola, Ethiopia and Afghanistan between the mid-1970s and 1979.
These moves convinced many Americans that the Soviets were trying to take advantage of American restraint after Vietnam and led to repeated American charges of Soviet expansionism.
The fact this perception was largely shared by the Chinese leadership accelerated US-China rapprochement during the Carter years, and fuelled Soviet strategic fears it was increasingly encircled by an anti-Soviet coalition headed by the US and China.
At the same time, the election of Jimmy Carter in November 1976 brought a new emphasis on human rights in the US, a development which the Brezhnev regime in Moscow viewed as a barely veiled attempt to ``interfere in the domestic affairs'' of the Soviet Union and its allies.
Arms control was a major casualty of deteriorating Soviet-American relations. The Soviet deployment of medium range SS-20 missiles in East Europe in 1977 prompted Nato in late 1979 to respond with a commitment to deploy Pershing and Cruise missiles in West Europe to directly counter the perceived new Soviet threat to that region.
Meanwhile, the signing of a Salt 2 agreement was delayed until June 1979, but efforts by the Carter administration to ratify the deal were effectively derailed by the Soviet invasion of Afghanistan five months later.
That event ended the era of detente and marked the resumption of renewed superpower confrontation, a development dubbed the Second Cold War.
By 1983, respected observers like George Kennan, the architect of US containment policy towards the USSR, publicly warned that the two superpowers were locked in a ``march towards [nuclear] war''.
Yet, by 1988, Soviet-American relations were at their best since 1945, and President Ronald Reagan was able to assert in Moscow that the Cold War belonged to the past.
It should be added detente's legacy played a significant role in shaping the new direction of Soviet-American relations.
First, while the Helsinki Final Act was widely seen as a ``sell-out'' in the United States, the Brezhnev regime had signed a treaty that recognised human rights across Europe, and this helped to intensify political dissent both in the Soviet Union and satellite states in East Europe, especially during the 1980s.
Second, the Soviet attempt to project power in the Third World at America's expense in the late 1970s turned out to be a classic case of military and economic overstretch. Interventions in Angola, Ethiopia and Afghanistan embroiled Moscow in three expensive quagmire conflicts, and helped Ronald Reagan, the anti-communist Republican presidential candidate, win by a landslide in 1980.
Third, ``system modernisers'' such as Mikhail Gorbachev within the ruling Soviet Communist Party had supported detente with the US, and were angry that the ageing Brezhnev leadership had contributed to circumstances in which the new Reagan administration in 1981 embarked upon a huge military build-up and increased the costs of Cold War competition at a time when the Soviet economy was already languishing.
In short, detente served as a catalyst in reframing the Cold War. By facilitating dissent in the Soviet bloc, fostering strategic miscalculations by the Kremlin, and strengthening the reformist wing of the ruling Communist Party, detente helped to create a political opening for Mr Gorbachev to assume power in 1985.
It was Mr Gorbachev's foreign policy revolution - radically improving Soviet ties with the US and China - that was pivotal in bringing the curtain down on the Cold War.
Robert G. Patman is a professor of international relations in the department of politics at the University of Otago.
