FOR 91-year-old Henry Kissinger, establishing a stable, balanced world order has been the overarching goal of his extraordinary life and career. “World Order” is also the title, not coincidentally, of his important new book, further affirmation of his place as one of the most distinguished foreign policy thinkers and diplomats in American history.

Kissinger returns to Harvard University this week, where he first made his mark as a brilliant young student and professor, following his service in World War II. He will talk with students about his most challenging negotiations with China’s Mao Zedong and Zhou Enlai, the Soviet Union’s Leonid Brezhnev and the leaders of Israel, Syria, and Egypt after the October War of 1973.

This “Lion in Winter,” as the Aspen Institute’s Walter Isaacson calls him, has authored a compelling book to help Americans make sense of a shifting, unsteady global order, and our own place in it.

And it is just in time. This year’s seismic international shocks confirm we are experiencing challenges to global peace that, left untended, could cause even greater violence and disorder in the year ahead. In the burning Middle East, the people’s revolutions of 2011 have largely failed, with nearly every country worse off as a result. Russian President Vladimir Putin’s continued aggression by subterfuge in Eastern Ukraine threatens Europe’s cherished democratic peace won with such promise at the end of the Cold War. A newly self-confident and assertive China is contesting the legitimate borders of the Philippines, Vietnam, and Japan in the South and East China Seas. And, an important new UN report warns that the impact of climate change may be greater than even the most sober scientists had thought.

These and other tests undermine, in Kissinger’s construct, the international order he rightly believes is a necessary precondition for global stability, prosperity, and peace. Together, they are challenging President Obama’s diplomatic dexterity in a way few would have imagined when he was reelected two years ago.

Kissinger worries that the durable and remarkably successful post-World War II order pieced together by Harry Truman, George Marshall, Dean Acheson, and others is now breaking down. For Kissinger, rebuilding that system is essential for a 21st century where the United States will remain the most influential country, but will need to share power with China, Russia, India, and others. Americans will need to help manage this global order through a mix of idealism and realism and resolve, as he wrote, “to act in both modes.” This middle path is imperative to restore peace and to avoid a potentially catastrophic superpower struggle.

These takeaways from Kissinger’s book speak directly to what I believe is Obama’s central challenge in his last two years in office. The United States must rediscover its self-confidence as the lead international actor. We must honor American ideals by opposing Russian aggression in Ukraine and Chinese adventurism in Asia while doing what we can on a selective basis to contain violence in the Middle East.

At the same time — here is where realism comes in — we must also keep lines open to Moscow and Beijing on issues where they have great influence — climate change, terrorism, Iran, and North Korea. Despite our many differences with the Russians and Chinese, we simply can’t operate in isolation from them. This generational challenge is rooted in intellectual and historical terrain that Kissinger may understand better than any other American. The United States can’t afford to leave the world’s center stage that Republican and Democratic presidents built because, in Kissinger’s warning, “reconstruction of the international system is the ultimate challenge to statesmanship in our time.” Words of wisdom from a remarkable American.

Nicholas Burns is a professor of the practice of diplomacy and international politics at Harvard’s Kennedy School of Government. Follow him on Twitter @rnicholasburns.