How did Nixons policy of détente develop under the administrations of Gerald Ford and Jimmy Carter?
The policy of détente was formulated during the Nixon Administration primarily by Henry Kissinger, the National Security Advisor and later Secretary of State under Nixon and Gerald Ford. Nixon had sought improved relations with the Soviet Union under Leonid Brezhnev in order to bring about nuclear arms reductions, decreased tensions in the developing world, and above all an end to the war in Vietnam. Nixon staged a historic visit to China, negotiated a (temporary, as it turned out) peace in Vietnam, and concluded the Strategic Arms Limitation Treaty (SALT) with the Soviet Union. Kissinger remained as Secretary of State under Gerald Ford, but the equilibrium established by détente was threatened by the collapse of the Geneva Accords when North Vietnam invaded and conquered the South. Ford, along with Brezhnev, signed the Helsinki Accords, which essentially recognized the borders of Western Europe as well as the Communist regimes in the East.
Under President Jimmy Carter, détente became harder to sustain. Carter made a commitment early in his presidency to human rights, and criticized the lack of commitment to this issue on the part of the Soviets. Indeed, under Carter, the commitment to détente began to give way to a more strident foreign policy. Carter began a significant buildup of the U.S. military, one which would continue under his successor Ronald Reagan. It can be argued that détente came to an end for good with the Soviet invasion of Afghanistan in 1979. In 1980, the election of Ronald Reagan saw the arrival of a President who based his campaign in part upon the idea that détente was immoral, an agreement to coexist with what he would later call an "evil empire" that was inconsistent with American values. So certainly by 1981, détente was a thing of the past.