We are fast approaching grand-strategy season in Washington. Within the next few weeks, the Obama administration will release both its Quadrennial Defense Review and new updated National Security Strategy. These documents often contain the essential strategic ideas—about goals and priorities, threats and opportunities, resources and constraints—that guide an administration’s statecraft. And because they do, they inevitably provoke debate about that administration’s grand strategy—whether it actually has one, what its major tenets are and what prospects for success it has.

They will also invariably provoke comparisons to the grand strategies of administrations past—to the origins and evolution of containment under Harry Truman, to the strategic retrenchment pursued by Nixon and Kissinger, to many, many others. And given that 2014 marks the twenty-fifth anniversary of the ending of the Cold War, there will almost certainly be comparisons to the grand strategy of the president who arguably did as much as any American leader to end that conflict: Ronald Reagan.

A quarter-century after he left office, Reagan remains a polarizing figure. Admirers have celebrated him as a master grand strategist who used geopolitical pressure and moral clarity to bring the Soviet Union to its knees. Detractors have argued that there was no Reagan grand strategy to speak of, and that the fortieth president was more fortunate in his timing than prescient or visionary in his statecraft. In recent years, the declassification of reams of U.S. documents from this period has made it possible to better assess Reagan’s legacy, and to more effectively understand what insights his presidency offers for today’s grand strategists.

As I outline in my new book, What Good is Grand Strategy?, Reagan did come to power with a collection of key strategic ideas already in mind: that the Soviet Union was militarily strong but ideologically, economically, and politically fragile; that a determined Cold War offensive could throw Moscow on its heels and allow Washington to regain the geopolitical initiative; and that a period of assertiveness and confrontation could actually set the stage for a longer-term move toward negotiation and the winding down of the East-West conflict on American terms. Once in office, Reagan codified these ideas in major national-security documents, and they informed the essential aspects of his wide-ranging assault on Soviet power: a massive military buildup, aid to anti-communist regimes and insurgents in the Third World, economic and political pressure on the Soviet system itself, and other measures. As National Security Adviser William Clark wrote, the goal was to “re-establish American ascendancy” and give the United States powerful geopolitical leverage.

During Reagan’s first term, these measures were extremely effective in raising the costs of Soviet foreign policy, increasing the strains on an already hobbled empire, and achieving a remarkable shift in the trajectory of the Cold War. Yet contrary to Reagan’s hopes, they did not convince Soviet leaders to moderate their policies or look for an accommodation with the United States. Quite the opposite, in fact: the very aggressiveness of Reagan’s strategy frightened the Kremlin leadership, reduced the near-term prospects for diplomacy, and contributed to a very dangerous escalation of East-West tensions. The most perilous moment came in late 1983, when Soviet leaders may have briefly mistaken major NATO military exercises for real preparations to launch a war against the Warsaw Pact.

In late 1983 and early 1984, Reagan thus made a significant tactical recalibration. He did not abandon his long-term goals, and he would continue to exert pressure on Moscow through the end of his presidency. But he also toned down his often-incendiary rhetoric, earnestly called for an expanded East-West dialogue, and made clear that Soviet moderation would be reciprocated by the United States. From this point onward, Reagan’s statecraft included both sticks and carrots: it emphasized efforts to preserve American strength and leverage, but also measures to conciliate, reassure, and even build a degree of personal rapport with his Soviet counterparts.

As both U.S. and Soviet documents indicate, it was this shift that allowed the administration to so productively engage Mikhail Gorbachev during the late 1980s. To be sure, much of the improvement in U.S.-Soviet affairs owed to Gorbachev’s determination to reduce defense costs and address the metastasizing cancer within the Soviet system. Yet Reagan’s policies also played a key role. He and Secretary of State George Shultz maintained a hard enough line so that Gorbachev could get the “breathing space” he wanted only by making real changes in Soviet policy. But they also constructed a climate of respect and even trust with Gorbachev, and they continually assured the Soviet leadership that constructive actions would bring about a better relationship with the West. In short, the administration underscored Gorbachev’s positive and negative incentives to shift course, and thereby encouraged a transformation of the Cold War.

That change was nothing short of astounding. By the end of Reagan’s presidency, the same man who had called the Soviet Union an “evil empire,” had cooperated with Gorbachev to produce an unprecedented arms control pact (the Intermediate-Range Nuclear Forces Treaty) that eliminated an entire category of nuclear weapons, to secure a Soviet withdrawal from Afghanistan and other parts of the Third World, and to improve the overall bilateral climate so much that leaders on both sides were now proclaiming the Cold War’s end.

So what does all this mean for understanding Reagan, and the lessons his presidency offers? First, Reagan was a leader who remains misunderstood by admirers and detractors alike. Reagan’s critics often ignore the fact that he did have a long-range vision for dealing with Moscow, and that the pressure he exerted on a vulnerable Kremlin empire was crucial to reversing the tide of the Cold War and achieving a favorable resolution of that conflict. But his more hard-line hagiographers frequently miss just how badly Reagan’s early policies exacerbated international tensions, and how essential his turn toward conciliation was in facilitating U.S.-Soviet diplomacy. Reagan was both a hawk and a dove, something that still eludes many observers of his record.

Second, Reagan’s experience demonstrates that vision and adaptation are both crucial to good grand strategy. Reagan foresight and his consistent emphasis on strength were central to his achievements in dealing with the Soviet Union. So too, though, was his willingness to learn from his early excesses and shift to a less aggressive-looking posture from late 1983 onward. As Reagan came to understand, an effective grand strategy requires a firm set of core priorities and principles, but also flexibility in turning those principles into effective policies. The same holds true today. American leaders need a clear sense of where they are trying to go in a complex and often-surprising international environment, but they must remain agile and adaptive in figuring out how to get there.

Third, and perhaps most important, Reagan’s presidency confirms a timeless geopolitical truth, which is that carrots and sticks go best together. Reagan could not have succeeded without imposing great strain on the Soviet Union, but neither could he have succeeded without showing Gorbachev that accommodation was a viable and attractive option.

Likewise, current American leaders will not prosper in dealing with rivals like Iran, or potential rivals like China, without manifesting the strength that is necessary to back up U.S. policies and interests. But they will also fail if they do not combine power and leverage with intensive diplomatic engagement, and with an ability to bring positive inducements to the table as well. Twenty-five years after Reagan left office, this particular lesson of his grand strategy remains as relevant as ever.

Hal Brands is an Assistant Professor in the Sanford School of Public Policy at Duke University. His most recent book is What Good is Grand Strategy? Power and Purpose in American Statecraft from Harry S. Truman to George W. Bush, just released by Cornell University Press.