Larry Diamond has made it his life's work both to study democracy and to advise dissidents fighting autocracy around the world. But when Donald Trump won the presidency by openly rejecting basic democratic norms, this lifelong scholar of democracy's struggles abroad felt a horrible sense of danger at home. As Diamond has long chronicled, democracy expands and retreats in waves. From the 1970s into the 1990s, the "third wave" saw democracy spread through Europe, Latin America, Asia, and Africa and attempt to take root in the former Soviet empire. But since 2006, Diamond has tracked a global democratic recession. By 2016, illiberal rulers were eroding democracy in Hungary, Poland, Turkey, the Philippines, and more, while China and Russia--the world's leading autocracies--grew increasingly bold and bullying. And with Trump's election, the global retreat from freedom spread from democracy's margins to its heart. Diamond's core argument is stark- The defense and spread of democracy has relied for decades on U.S. global leadership, including its alliances with advanced democracies in Europe and Asia. If America does not reclaim its traditional place as the keystone of democracy, today's authoritarian trend will accelerate into a "third reverse wave" of democratic breakdowns. That wave could become a tsunami. And that could let Vladimir Putin, Xi Jinping, and their admirers turn the 21st century into a dark time of surging authoritarianism. But it's an ill wind that brings no good with it. Free governments can defend their values; free citizens can exercise their rights. Diamond explains how we can make the Internet safe for liberal democracy, how we can exploit the soft, kleptocratic underbelly of dictatorships, and how we can revive America's degraded democracy. He offers concrete, deeply informed suggestions for policymakers and citizens alike, including ways to fight polarization, reduce the influence of money, combat partisan gerrymandering, expand voter turnout, and negate the electoral college. We are at a hinge in history, between a new era of tyranny or a new age of democratic renewal, and freedom's last line of defense is still "We the people."