For eight decades, the United States has built a global order around its interests and values. In 100 days, Donald Trump has torn it down.
The United States remains, by most measures, the world's most powerful country and Trump has vowed to strengthen it further by aggressively promoting domestic business and ramping up military spending.
But the Republican billionaire offers a far more unilateralist vision than any modern US president.
Reviving views long seen as antiquated, Trump has vowed US expansionism, setting sights on the Panama Canal, Greenland and Canada, which he has belittled as the "51st state."
In another throwback, Trump imposed sweeping tariffs on both friends and foes -- a step that was mostly suspended following a market rout, except against China, which is seen as Washington's top adversary.
Yet the property tycoon-turned-president who boasts of his dealmaking skills has also been open to reaching transactional agreements with rivals, including China and Russia.
He and Vice President JD Vance have been less committed to maintaining post-World War II security guarantees to allies, especially in Europe, seeing the region's developed countries as commercial competitors who are freeloading on US defense.
"His initiatives are shattering what we have known, certainly since World War II," said Melvyn Leffler, a historian of US foreign policy at the University of Virginia.
"I think Trump is a return to late 19th-century Social Darwinism, in which he believes all nations are embroiled in a struggle for survival of the fittest," he said.
"I think what is most fundamentally important is that Trump does not believe in the concepts of mutual interdependence, shared values and common interests, even with allies."
Mixed 'peacemaker' record
Trump, showing a distaste for soft power, has killed more than 80 per cent of US overseas assistance and has eyed major cuts in diplomatic staff in Africa.
But he also said in his January 20 inaugural address that his ultimate ambition was to be a "peacemaker" -- a role in which his success rate is decidedly mixed.
Trump had vowed to end the Ukraine war on his first day back in the White House.
On Friday, Secretary of State Marco Rubio said that the United States may "move on" from seeking a Ukraine solution, after talks initiated by Washington have failed to lead to concrete outcomes.
Russian President Vladimir Putin has rebuffed calls for a complete truce, even as he relishes the shift in US tone on Ukraine -- seen most dramatically in a February 28 White House showdown where Trump and Vance publicly accused President Volodymyr Zelensky of being an ingrate.
Trump spoke proudly of how his globe-trotting envoy Steve Witkoff helped secure a Gaza ceasefire shortly before the inauguration, using the outline of a plan prepared by outgoing president Joe Biden's team.
Israel has now resumed military operations in Gaza, vowing a death blow to Hamas over its October 7, 2023, attack, and blocking aid to the Palestinian territory, leading to the worst humanitarian situation since the start of the war.
Trump, however, appears for the moment to have restrained Israel from a strike on Iran, with Witkoff holding two friendly meetings with Tehran on seeking a deal on its contested nuclear program.
Turning point?
After defeating Trump in 2020, Biden vowed to restore the United States' global role, especially with allies.
The extent of the tumult induced by Trump in his second term -- and the reaction to it -- is far wider-reaching.
After Trump's dressing down of Zelensky, EU foreign policy chief Kaja Kallas said that "the free world needs a new leader."
Faith in US policymaking has historically been so strong that the dollar gains during times of crisis, with investors turning to US Treasury bonds.
Since Trump's inauguration, the dollar has slipped nine per cent against a basket of other major currencies.
The trend is largely welcomed in Trump's circles. Vance has blamed foreign investors for keeping the dollar high at the expense of US manufacturers.
Prime Minister Lawrence Wong of Singapore, long a key US partner in Asia, said Trump's tariff announcement showed that "the era of rules-based globalisation and free trade is over" after having America as its "anchor" for eight decades.
Wong noted that the United States has fared better than other advanced countries but acknowledged the Americans who lived in "hollowed-out towns" and felt the economy is "fundamentally broken."
Leffler, the historian, said that many Americans had lost faith in the system based on a globalised economy, promoted by presidents of both major parties.
With China also on the rise, Leffler expected Trump's actions to "portend a new trajectory" in world affairs.
"I do not believe the United States will return to the same type of liberal, global, hegemonic order that has existed more or less from 1945," he said.
