The Donald Trump-Kim Jong-un "summit of the century" was a harbinger of a new age.

We are witnessing a shifting global order marked by great power politics; self-interest; deal making; pragmatism increasingly devoid of supposed universal ideas of morality or human rights.

The strongman (and he is a man) is ascendant, tightening his grip in authoritarian regimes or taking power at the ballot box in democracies.

This is a break from the so-called "rules-based order" built on fair elections, free trade, open borders, security alliances, pooled sovereignty, that had grown and spread across much of the world, post World War II, and for a while appeared triumphant at the end of the Cold War.

At the time, political scientist Francis Fukuyama called it "the end of history".

If that is the case, history is back, bringing with it resurgent nationalism, sectarianism, tribalism and populism.

Sorry, this video has expired Donald Trump and Kim Jong-un address reporters

Over the past two decades, the liberal order has been struck multiple blows: radical Islamic terrorism and the resultant war on terror; the rise of China and the 2008 collapse of the global financial system.

All have tested the resilience of the West and the resolve to defend liberal values.

Now liberalism is in retreat; globalism appears exhausted and cosmopolitanism is looked on as the vanity of the elites.

We are witnessing a blowback: anger at inequality; resentment of immigration; loss of faith in institutions.

'Bruised and disillusioned'

US President Donald Trump is a product of this age; in a week when he has insulted allies and praised a dictator, Mr Trump has revealed how he not only grasps this new world but how he intends to navigate it.

America first is the Trump doctrine.

He is banking on maintaining American power. Not by reinforcing US global leadership but by managing a retreat from it.

Mr Trump can strike a deal with North Korea because it is in his interest, but then cancel joint military exercises with South Korea and float the idea of drawing down the numbers of American troops because the cost is too high.

Trade, immigration, security — these are just some of the emerging battlegrounds in this new geo-political landscape.

US President Donald Trump arrives aboard Air Force One from Singapore. ( Reuters: Jonathan Ernst )

Political scientist Bruno Macaes has captured this age in an essay for the latest American Interest magazine America's Pivot from the West.

"America is bruised and disillusioned … looking for something less ideal," Macaes said. "The United States is becoming a realist power in a world of many idealisms."

Historian, Stephen Kotkin, writing this week in the journal Foreign Affairs, reminds us that "states rise, fall and compete with one another".

"Great-power politics will drive events, and international rivalries will be decided by the relative capacities of the competitors, Kotkin said.

We are at a critical juncture, as Kotkin says, "authoritarianism is all-powerful yet brittle, while democracy is pathetic but resilient".

Is Trump the right leader for these times?

To his detractors, Mr Trump is almost solely responsible for dismantling American hegemony.

In the New York Times, deputy director-general of the institute for Strategic Studies, Kori Schake, says "we may look back at the first weeks of June 2018 as a turning point in world history: the end of the liberal order."

She accuses Mr Trump of, "reckless disregard for the security concerns of America's allies, hostility to mutually beneficial trade and wilful isolation of the United States".

In truth, what writer and journalist Fareed Zaharia has called the "post-American world", has been a slow unravelling.

He first wrote those words more than a decade ago, describing a world not devoid of American power but a new multi-polar landscape, one where others have narrowed the gap, compete for influence and promote their interests.

Barack Obama's presidency spanned much of this era, he was seen as a defender of the liberal order, but his record is hardly exemplary.

He left the world with:

the Islamic State group having carved out a mini caliphate,

the Islamic State group having carved out a mini caliphate, Iran and Saudi Arabia locked in a battle for Middle East influence and backing rival sides in a proxy war in Yemen,

Iran and Saudi Arabia locked in a battle for Middle East influence and backing rival sides in a proxy war in Yemen, Syria torn apart by civil war,

Syria torn apart by civil war, Bashar Al-Assad using chemical weapons on his own people (a red line Obama drew then failed to enforce),

Bashar Al-Assad using chemical weapons on his own people (a red line Obama drew then failed to enforce), Russia reasserting its influence,

Russia reasserting its influence, Putin annexing Crimea,

Putin annexing Crimea, China militarising the disputed islands of the South China Sea,

China militarising the disputed islands of the South China Sea, North Korea becoming a nuclear-armed state,

North Korea becoming a nuclear-armed state, and the European Union beginning to unravel amid the resurgence of the far right.

For all his fabled eloquence and charisma — not to mention his Nobel peace prize — that is the Obama foreign policy legacy.

With such a record would Trump get a pass mark?

Mr Trump is already being criticised for even deigning to meet Kim Jong-un, yet Mr Obama also offered to sit down with America's enemies "without preconditions".

The Obama foreign policy legacy is hardly exemplary, Stan Grant writes. ( AAP: Rick Roycroft )

Mr Trump's critics accuse him of giving too much while receiving little in return, and his flattery of Mr Kim — a man accused of crimes against humanity — and saying he was honoured to meet him was galling to many.

But the historic meeting has offered a glimmer of hope for millions locked inside the secretive regime of North Korea or in the firing line of Kim's missiles.

It may have, in the words of South Korean President Moon Jae-In, built a "platform for peace".

Mr Trump is being judged against a liberal order that appears redundant and one the President himself gives little indication of believing in.

These are dangerous times and Mr Trump — at his worst, impetuous, provocative and reckless — may imperil us all.

At his best, he has displayed sharp political instincts and a willingness to shake up "business as usual" orthodoxy, that may yet yield results.

This past week, Mr Trump has shown us the potential for hope and disaster.

Sorry, this video has expired Donald Trump and Kim Jong-un jointly sign memorandum

Speaking to ABC's Matter of Fact in Singapore, New York Times national security correspondent David Sanger identified a key concern, that Mr Trump prefers transactional relationships over alliances.

In the wake of the Trump-Kim summit, Britain's New Statesman magazine wrote Mr Trump prefers dictators to democratic leaders, that the Trump Doctrine sees other nations, "not as allies but as competitors in a zero-sum game".

Geo-politics has shifted: Pax Americana was, in balance, good for the world. We are richer and enjoy more freedom than at any time in human history. But the western conceit was that other countries like China and post-Cold-War Russia would become more like us. They haven't.

Mr Trump is President of the most powerful nation on the planet, but it is weary and there are viable challengers and threats. He confronts a world as it is and not as many others would wish it to be.