As in the past, the day will be cold. Melania will hold the Bible. The kids will stand by proudly. The new President will recite his lines carefully, smile broadly and change history. And American international leadership, a constant since 1945, will end with the presidential inauguration of Donald J. Trump on Jan. 20, 2017.

That’s not because Trump is bound to fail where his predecessors have succeeded. Given the rise of other countries with enough power to shrug off U.S. pressure–and other factors, like the ability of smaller powers to punch above their weight in cyberspace–this moment was inevitable. America will remain the sole superpower for the foreseeable future–only the U.S. can project military muscle, economic clout and cultural influence into every region of the world. But Trump’s election marks an irreversible break with the past, one with global implications.

For at least the next four years, America’s interactions with other nations will be guided not by the conviction that U.S. leadership is good for America and the world but by Trump’s transactional approach. This will force friends and foes alike to question every assumption they’ve made about what Washington will and will not do. Add a more assertive China and Russia to the greater willingness of traditional U.S. allies to hedge their bets on American plans and it’s clear that we’ve reached a turning point. Trump is not an isolationist, but he’s certainly a unilateralist, and a proudly selfish one. Even if he wanted to engage the G-7 or G-8 or G-20 to get things done–and he doesn’t–it has become unavoidably obvious that the transition toward a leaderless world is now complete. The G-zero era I first predicted nearly six years ago is now fully upon us. No matter how long Trump remains in the White House, a crucial line has been crossed. The fallout will outlive his presidency, because Trump has proved that tens of millions of Americans like this idea.

Trump’s “America first” approach fundamentally changes the U.S. role in the world. Trump agrees with leaders of both political parties that the U.S. is an exceptional nation, but he insists that the country can’t remain exceptional if it keeps stumbling down the path that former Presidents, including Republicans and Democrats, have followed since the end of World War II. Washington’s ambition to play the role of indispensable power allows both allies and rivals to treat U.S. taxpayers like chumps, he argues. Better to build a “What’s in it for us?” approach to the rest of the world. This is a complete break with a foreign policy establishment that Trump has worked hard to delegitimize–and which he continues to ostracize by waving off charges of Russian interference in the election and by refusing the daily intelligence briefings offered to all Presidents-elect. American power, once a trump card, is now a wild card. Instead of a superpower that wants to impose stability and values on a fractious and valueless global order, the U.S. has become the single biggest source of international uncertainty.

And don’t expect lawmakers to provide the traditional set of checks and balances. It’s not just that the Constitution gives the President great power to conduct foreign policy. It’s also that Trump has succeeded politically where his party’s establishment has continually failed, and as long as he remains popular with the party’s voters, many junior Republican lawmakers will answer to their President rather than to their leaders on Capitol Hill. Expect Trump to use the bully pulpit with a vengeance, often at 140 characters or less, to try to set new rules and rally the faithful to follow his lead.

As for special interests, Trump isn’t much beholden to Wall Street, Silicon Valley or Big Business, since most didn’t support him. Those in the tech class, in particular, are the most liberal of the U.S. business elite, and Trump’s intense criticism of Apple for resisting FBI efforts to hack into the cell phones used by the attackers in San Bernardino, Calif., previews plenty of fights to come between the Trump White House and Silicon Valley. Trump has essentially charged Big Business with treason and threatens to punish–individually–those companies that ship jobs overseas.

He hasn’t yet taken the oath of office, but Trump (and Trumpism) have already begun to create turmoil abroad. In Europe, the new President’s full embrace of Brexit sets teeth on edge in many capitals, and his friendly approach to Russia leaves European governments scrambling for security alternatives to NATO. Transatlantic relations have reached their lowest point since the 1930s. In Asia, his confrontational attitude toward China will bolster U.S. ties with allies like Japan and India that have long-term reasons to resist China’s rise, but it has already made it that much harder to manage Washington’s relations with Beijing, the most important relationship for the future of the global economy. It will also complicate any bid by the U.S. and China to work together, or at least in parallel, when North Korea finally becomes a red-alert-level emergency–which it almost certainly will.

But the election of Donald Trump is just the latest source of G-zero uncertainty and turmoil. Few leaders in today’s world, particularly in Europe, have enough popularity to get anything done, and the current wave of populism sweeping through many E.U. countries calls into question the legitimacy of institutions and governing principles in the world’s most advanced industrial democracies. France will head to the polls in 2017, led by a President too weak to stand in an election in which a leading contender wants to pull the country out of the E.U. In Britain, with European negotiators and members of her own party intent on driving exceptionally hard bargains, it’s far from clear that Prime Minister Theresa May can navigate her divided country through (at least) two years of Brexit negotiations.

In Germany, the lack of any appealing alternative will probably keep Angela Merkel as Chancellor, but domestic backlash against her open-door policy for Middle East migrants will leave her much weakened. In Italy, the failure of Matteo Renzi’s political-reform referendum has upended politics, dooming the country’s 64th government in 70 years. Greece’s financial problems are far from finished. The E.U. is in for a rough ride in 2017, even if its deal with Turkey to sharply limit the surge of Syrian refugees into Europe holds, helping avoid a repeat of the tidal wave of desperate people that roiled E.U. politics.

While there are places where the risk is overblown, the outlook isn’t much brighter in the developing world. The latest round of tensions between India and Pakistan over Kashmir has made headlines, but both governments want to avoid an escalation of violence that might hurt them at home. In Indonesia, the world’s largest Muslim country, the capital city’s Christian governor has aroused Muslim fury, but President Joko Widodo continues to promote economic reform and much-needed investment in the country’s infrastructure.

China’s top leaders have become increasingly confident in their ability to maintain their monopoly on domestic political power and to develop stronger international relationships with willing partners. But a scheduled leadership transition next fall might create much higher levels of stress in Beijing and a more belligerent attitude from its leaders–particularly if China’s economy begins to show unexpected vulnerability. With that backdrop, Trump’s hostile approach, including treating U.S. policy on Taiwan as a card to play, will generate anxiety.

Vladimir Putin remains firmly in charge in Moscow, and Trump’s win provides an unexpected bonus in better relations with the White House. We might even see an easing, if not an end, of Western sanctions in 2017. But oil prices won’t reach the heights that boosted the Russian economy a decade ago, which exposes a longer-term vulnerability for which Putin has no credible answer. He has more than enough political and financial capital to avoid serious trouble in 2017, but the long-term erosion of Russia’s power and financial reserves will eventually give Putin good reasons to create international distractions. In Mexico, hostility toward (and from) Trump is already stirring up trouble. And economic crisis and political confrontation are headed toward a potentially violent climax in Venezuela.

Turkey’s Recep Tayyip Erdogan, a would-be Putin bent on expanding his authority, has expressed growing hostility toward E.U. leaders who depend on his goodwill to limit migrant flows. South Africa’s scandal-plagued President continues to ignite partisan passions. Protests, a staple of the country’s political culture, have again turned violent.

No region feels the G-zero pressure more acutely than the Middle East. In Saudi Arabia, low oil prices, Iran’s release from sanctions, a lack of reliable friends and rivalries within the royal family are creating ever higher levels of stress. The killing continues in Yemen and in Syria, where Bashar Assad has all but conquered Aleppo. Finally, the military defeat of ISIS will scatter surviving fighters across the Middle East, North Africa, East Africa, Southeast Asia, Europe, Russia and elsewhere in search of opportunities to wage jihad on new battlefields.

While America’s withdrawal will create uncertainty, no one is rushing in to fill the vacuum. China’s investments in Asia, Africa and Latin America boost Beijing’s influence in dozens of countries, and Trump’s renunciation of the Trans-Pacific Partnership, an enormous trade deal, gives China an excellent opportunity to expand its web of regional trade ties. But Beijing can’t match Washington’s military reach or cultural appeal. It’s not a major producer of energy, food or the latest advanced technology. And China’s leaders have their hands full at home. They must ensure that the nation’s economy continues to develop and modernize to maintain their monopoly of domestic political power. The reality is that there is no emerging power ready, willing and able to take the leadership role the U.S. will no longer play.

Around the world, populism will decentralize power away from central state actors toward local officials, at the expense of international cooperation. This anger undermines the authority of supranational organizations–the E.U., NATO, the U.N. The pace of technological change threatens the ability of governments to govern. An ever growing number of major decisions are taken by nonstate actors–data-hungry companies, hackers, political interest groups and terrorists.

The international order itself is unraveling. In the past eight years alone, the world has seen the worst financial crisis in decades, a global recession, a historic debt crisis in the euro zone, a wave of unrest across North Africa and the Middle East, civil war in Syria, a migrant crisis that calls into question the future of Europe’s open borders, war between Russia and Ukraine, Brexit, an explosion of cyber aggression and the election as U.S. President of one Donald Trump. Call it geopolitical creative destruction or just the sound of things falling apart, but the grinding of G-zero gears has become too loud to ignore.

In the short term, 2017 will have more than its share of decisive political moments. France will stage the most anticipated presidential election in years this spring, with the country’s future as a European pillar at stake. Marine Le Pen of the far-right National Front hopes to ride Europe’s populist wave toward victory–and sound the death knell for the entire E.U. project. In the fall, Merkel, the last-standing champion of Western liberal values, seeks re-election as Germany’s Chancellor. Both countries fear that Russian hackers will try to disrupt their elections, just as Moscow is suspected of having done in the U.S.

There will also be a presidential election in Iran that might well bring tensions between reformers and hard-liners in that country to a head. Russia, Saudi Arabia, Venezuela and others will continue to seek solutions to the existential threat posed to their economies by persistently low oil prices. Angry words between Europe and Turkey will threaten a new surge of migrants across E.U. borders. China’s leadership transition will make Beijing a more unpredictable player in regional and international politics.

And President Donald Trump will lead the United States of America into uncharted waters.

This appears in the December 26, 2016 issue of TIME.

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