IN THE EARLY 1970s, Richard Nixon and Henry Kissinger wanted to forge a new relationship with the Soviet Union. In the midst of the war in Vietnam, a slowing economy, and racial strife at home, they felt that the United States couldn’t continue to bear the limitless costs of waging the Cold War. Their solution was détente, a relaxation of tensions with the Soviets that would allow Nixon to reduce military spending and extricate the nation from Indochina.

Détente, however, meant that the U.S. government could no longer criticize the Soviets’ appalling human rights record. In the name of stable and friendly relations, American ideals were suppressed; justice was sacrificed for order. “I have no doubt that Soviet Jews as a group are severely disadvantaged,” Kissinger said dispassionately to a colleague in 1969, “but there is virtually no way in which we as a government can exert pressure on the Soviet Union to ease their plight.” In fact, he continued, American hectoring of the Soviet Union would be “counterproductive” because the Soviets “are exceptionally defensive about the Jewish problem, and inevitably regard any official U.S. Government action on the subject as an attempt to interfere in Soviet internal affairs”—which, of course, is precisely what détente’s critics had in mind. Even worse, the Kremlin then used détente as cover to launch a renewed assault on the basic rights of their Jewish citizens—and many Christians, too. Unable to practice their religion, Soviet Jews pressed to emigrate to Israel; the Kremlin wouldn’t let them, virtually imprisoning a people because of their faith.

This didn’t sit well with many Americans, who sprang into action. They bombarded the White House with letters and telegrams of support for Soviet Jews and opposition to détente, and they picketed Kissinger’s activities. They also enlisted members of Congress from both parties, such as Senators Henry M. “Scoop” Jackson and Jacob Javits and Representative Charles Vanik, who backed the campaign for Soviet Jews enthusiastically. Nixon and Kissinger unwisely dismissed this bipartisan human rights campaign for religious liberty and freedom of movement. Instead of petering out, it grew dramatically and undermined popular support for détente among liberals and conservatives alike even though three presidents from both parties—Nixon, Gerald R. Ford, and Jimmy Carter—did everything they could to make it work.

In 1972, the anti-détente campaign achieved a notable success with the passage of the Jackson-Vanik Amendment to a trade bill. The Soviets’ greatest incentive to make détente work was access to the U.S. economy and U.S.-dominated international capital and credit markets; Nixon and Kissinger’s leverage, therefore, came from their ability to grant the Soviet Union Most Favored Nation (MFN) trading status that would allow them such access. However, only an act of Congress could bestow MFN status upon a country, and the mood in Congress was decidedly uncooperative. From the Senate, Jackson teamed up with Vanik in the House to make the extension of MFN status to the Soviet Union dependent upon a demonstrable improvement in their treatment of Jews, especially the right to emigrate to Israel. Knowing that they could command bipartisan majorities in both houses of Congress, and knowing that the Soviets would never consent to the meddling which their amendment demanded, Jackson and Vanik had effectively killed détente. As Soviet Ambassador to Washington Anatoly Dobrynin recalled, “no other single question did more to sour the atmosphere of détente than the question of Jewish emigration from the Soviet Union.” It was a question Nixon and Kissinger had never wanted to ask.

By 1979, détente had collapsed under the weight of its own internal contradictions. But Americans’ campaign for the religious rights of others continued apace. Democratic politicians like Senator Jackson and Massachusetts Congressman Father Robert F. Drinan—the first priest elected to Congress—worked in tandem with Republicans to call attention to the anti-religious human rights abuses of communist regimes in Eastern Europe and the Soviet Union. In turn, nongovernmental organizations like Human Rights Watch and the Christian Committee for the Defense of Believers’ Rights supplied Jackson, Drinan, and others with evidence smuggled out of Europe of communist abuses of religious liberty.

Nixon, Ford, and Carter handled domestic religious politics poorly. And there things stood when Ronald Reagan became president in 1980. Reagan’s solution was to blend religion with foreign policy in a way that would promote American values while also serving the U.S. national interest. The result was the end of the Cold War.

This solution, however, did not come easily, and Reagan initially stumbled by promoting American exceptionalism, particularly the idea that America was God’s chosen nation, at the expense of religious liberty. In March 1983, in a major address to the National Association of Evangelicals, Reagan denounced the Soviet Union as an “evil empire” and called for a renewed effort to win the Cold War. “There is sin and evil in the world,” he reminded the NAE delegates, “and we’re enjoined by Scripture and the Lord Jesus to oppose it with all our might.” In that same speech, he condemned his domestic critics in the nuclear freeze movement, mostly Catholic priests and bishops, who assailed U.S. policies on strategic weapons and in Central America. Such rhetoric alarmed people around the world and created opposition to U.S. foreign policy at home and abroad.

But then Reagan pivoted to religious liberty instead of religious exceptionalism—at precisely the same time he began to explore a relaxation of tensions with Moscow—and he found his progress much easier. The same year as his “evil empire” speech—and, amazingly, two full years into his presidency—Reagan invited the Soviet ambassador, Anatoly Dobrynin, to the White House for their first-ever private conversation. To Dobrynin’s astonishment, Reagan wanted to discuss only one issue, and it wasn’t nuclear weapons, China, or anything else geopolitical. Instead, he wanted to ask the Soviet ambassador about the fate of a group of Soviet Pentecostals, known as the “Siberian Seven,” who had sought asylum in the U.S. Embassy in Moscow on the grounds of religious persecution.

They had been living in the embassy basement for almost five years. Thanks to another Massachusetts Congressman, Barney Frank, among others, they had also drawn the attention of human rights activists in the United States. Before entering the White House, Reagan had championed the Siberian Seven’s cause. Now, as president, and already thinking about détente and curious to see if the Soviets were too, he asked Dobrynin to help ease the Siberian Seven’s flight from the U.S.S.R. In return, he promised not to boast about it. Both sides, said Reagan, could use the quiet release of the Pentecostals as a confidence-building measure.

At the same time, Reagan encouraged his friend, the evangelist Billy Graham, to reverse his longstanding anti-communist politics, take his crusade to the Soviet Union, and talk with the Kremlin. By this time, Graham had softened his hardline anti-communist views out of fear that the Cold War was spinning out of control and leading the world towards a nuclear war. In promoting détente, both President Reagan and Reverend Graham emphasized the blessings of religious liberty, and its centrality to democratic reform without hectoring or condescending to the Soviets—and it seemed to work. If the Kremlin was willing to relax restrictions on the freedom of worship, they reasoned, it was likely to embark on other reforms. And if Soviet officials were indeed willing to permit religious liberty, even if at first only partially, then it was an important harbinger of the peaceful future that lay ahead.

“Our people feel it keenly when religious freedom is denied to anyone anywhere,” Reagan declared on a 1988 visit to Moscow, just as the Cold War showed signs of permanently thawing. “We may hope that perestroika will be accompanied by a deeper restructuring, a deeper conversion, a mentanoya, a change in heart, and that glasnost, which means giving voice, will also let loose a new chorus of belief, singing praise to the God that gave us life.” Reagan, it seemed, was able to have it both ways: peace and justice. The Cold War was coming to a close not through a final military campaign, but through the spread of religious liberty, democracy, and other human rights.

But it was not Reagan’s triumph alone. Behind him stood millions of Americans, from clergy to congregations, in churches and synagogues across the country, as well as members of both houses of Congress, from both parties and every strain of ideological persuasion. When Clinton and Bush spoke of America’s response to al Qaeda’s terrorism from the pulpit of the National Cathedral, then, they were not beginning a new tradition in U.S. diplomatic history, but tapping into a very old and very powerful one.

Andrew Preston is senior lecturer in American History at the University of Cambridge. He is the author of Sword of the Spirit, Shield of Faith: Religion in American War and Diplomacy, released in February from Knopf. In March, he presented a lecture at the John C. Danforth Center on Religion & Politics, entitled “The Religious Influence in American War and Diplomacy: A History.”