Yuri Gripas / Reuters

This week, the House Intelligence Committee will hold its first open hearing under the new Democratic majority. When I took over as chairman of the committee in January, there was no shortage of topics that would be obvious candidates for the committee to focus on—China’s growing might, Russian interference in our election, Turkey’s drift, or countless other threats. Our first hearing will not be on any of those topics, but rather on an issue that may surpass them all in importance, and yet underlies each: the rise of authoritarianism and the threat to liberal democracy around the world.

Ronald Reagan once called America the “shining city upon a hill.” Today, our light of freedom is shining less brightly. Across the globe, democracies are mired in an ugly brand of populism often directed against “the other,” and are displaying a troubling receptivity to autocracy as an alternative model of governance. If these trends continue, it will be a tragedy for humankind and a disaster for our national security.

The fight for freedom and democracy has been a long and arduous one. The blood of millions was spilled in the 20th century for the cause of democratic governance and respect for fundamental human rights. Out of the ashes of two world wars and the grinding decades of the Cold War, America looked across the globe and saw a world that seemed to be slowly, but irreversibly, becoming freer and more democratic. The world, it appeared, might finally become “safe for democracy,” in the words of President Woodrow Wilson.

Our optimism was once again misplaced. The past decade has demonstrated that democratic change is not inevitable, but must be doggedly pursued by free societies. At present, democracies are backsliding the world over, with threats to the rule of law, freedom of the press, and independent civil society growing ever more severe. The unipolar moment of the 1990s has given way to an emboldened Russia headed by Vladimir Putin and an increasingly assertive China led by Xi Jinping, both bent on promoting their own brand of authoritarian rule through a combination of military might, cyber–informational warfare and theft, and the skillful use of economic leverage.

In Caracas, Ankara, Budapest, Manila, Brasília, and elsewhere, strongmen have firmly grasped power. Rulers such as Viktor Orbán and Recep Tayyip Erdogan came to power through democratic means, but moved swiftly and brutally to centralize power and stamp out opposition. They have attacked the independent judiciary, the media, and the opposition political parties in their countries, waging campaigns of harassment, imprisonment, and violence. The Trump administration does not fully grasp the threat these trends portend to our national interest or what it means when treaty allies such as Hungary, Turkey, and the Philippines see their interests more closely aligned with those of our global adversaries in Moscow or Beijing than with those of the United States.

There is no single cause for democratic retrenchment, but tectonic shifts in the global economy, the advent of the internet and new modes of communication, and the refugee crisis have helped fuel populist backlashes that empower autocratic rulers. These enormously disruptive societal changes—imagine the invention of the printing press and the Industrial Revolution taking place simultaneously—have tested the capacity of representative government, which by design moves with deliberation and trends toward moderation.

At last week’s national-security conference in Munich, our allies questioned America’s commitment to our transatlantic alliance and our ideals. We must respond, clearly and without equivocation, in defense of our values and our democratic allies. We must be clear-eyed about these threats and recognize that human progress is not an inevitability, but will have to be won anew by each generation. Our diplomats, military, and intelligence agencies must have the support and resources they need to help America lead the free world, and to anticipate and respond when Russia, China, and others seek to extend their reach and undermine democratic societies.

In his resignation letter as secretary of defense, James Mattis defined the stakes, writing that it was “clear that China and Russia want to shape a world consistent with their authoritarian model.” He also issued what, for the famously stolid Mattis, amounts to a cri de coeur, writing that “while the U.S. remains the indispensable nation in the free world, we cannot protect our interests or serve that role effectively without maintaining strong alliances and showing respect to those allies.”

It is this call that Americans—Democrats and Republicans—must answer.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.