Gone are any pretences about saving the Iranian people. “They really are a nation of terror and hate,” Donald Trump says of Iran. Asked if he would like to help its people, he replied: “I’d like to, if they can behave, but they’ve been very menacing.” Perhaps even he sensed the counterproductive ugliness of this, hastily adding that they are “great people … smart, brilliant, energetic”.

It gets worse. Trump wrote on Truth Social that Iran had “plans of taking over the entire Middle East” and “completely obliterating Israel,” adding: “JUST LIKE IRAN ITSELF, THOSE PLANS ARE NOW DEAD!” Pronouncing the death of a nation hardly screams liberation.

Nor are these isolated flourishes. If Iran continues to block the strait of Hormuz, Trump threatens, the US will “take out easily destroyable targets that will make it virtually impossible for Iran to ever be built back, as a Nation, again”. Then, with apocalyptic relish: “Death, Fire, and Fury will reign upon them.”

While such language is meant to project strength, it portrays something else entirely. These are the morbid symptoms of a collapsing hegemony. Previous US presidents understood that domination required moral cover. Forty-five years ago, Ronald Reagan cast the US as “the exemplar of freedom and a beacon of hope for those who do not now have freedom”. Two decades later, George W Bush spoke of democracy as “the inborn hope of our humanity, an ideal we carry but do not own”.

These were always myths and deceptions. The US overthrew elected governments in favour of murderous dictatorships from Iran to Chile. From the napalming of Vietnam to the torture cells of Abu Ghraib, grievous crimes have always accompanied its power. But moral authority – however constructed – mattered. It functioned as a magnetic pole, drawing support from populations across the world.

The postwar Marshall plan was not an act of generosity to rebuild western Europe after Nazi barbarism, but a mechanism for binding western Europe into a US-led order. Voice of America and Radio Free Europe broadcast to the world narratives of US benevolence.

The United States Agency for International Development (USAID) combined humanitarian relief with the promotion of privatisation and market access for US business. The National Endowment for Democracy (NED) funded pro-western NGOs aligned with neoliberal economics.

USAID, of course, was gutted by Trump’s on-off “first buddy”, the far-right plutocrat Elon Musk, while the president’s attempt to defund NED was only reversed by Congress. All of this may seem irrational if maintaining US domination is your goal. But that misses the point about Trump’s strategic response to US decline.

Trump knows, however erratically, that US hegemony is drawing to a close. His national security strategy last year critiqued US foreign policy elites for believing “that permanent American domination of the entire world was in the best interests of our country”.

After the Soviet collapse, US elites concluded their economic model and military supremacy were unchallengeable – and behaved accordingly. The result was a chain of disasters: the financial crash, and strategic failures in Iraq, Afghanistan and Libya. Each crisis redistributed power away from the US, not least to China, which pursued state-led development while avoiding military quagmires.

Trump’s conclusion is stark: only brute force and bloodcurdling threats can arrest decline. Venezuela offers a telling example. After kidnapping its leader, he declared: “We are going to run the country,” adding that the proceeds of its oil would be controlled “by me, as President of the United States of America”. The message to its new president, Delcy Rodríguez, was explicit; “behave” – or face “a second strike”.

This is gangsterism fused with old-style colonialism. It repudiates the very language through which US power once justified itself. “The United States does not seek either political or economic domination over any other people,” Dwight Eisenhower insisted in 1957. Trump has no interest in such claims. He is content simply to seize what he can.

Hence his boast, after cutting off Venezuela’s oil shipments to an already besieged Cuba and contributing to the collapse of its electrical grid: “I can free it or take it, I think I can do anything I want with it.” This thuggery cannot be applied everywhere, of course, and nor will it be sustainable in the long term even where it succeeds. But that’s not Trump’s plan. His alternative to global hegemony is to apply brute force where he judges it most strategically valuable. That logic underpinned his assassination of Iran’s supreme leader, rather than triggering a wider war that has simply accelerated US decline.

We’ve also seen how the US will support useful allies to horrific ends. The facilitation of Israel’s genocide has eroded any meaningful boundary around violence; what once shocked is now routine.

That doesn’t mean Trump doesn’t have his own version of moral power. That has focused on promoting far-right parties across the west – but even many of their supporters object to Trump. In practice, his approach will deepen anti-Americanism and push even longstanding allies away from the US orbit.

As a strategy, it will not work. It may deliver piecemeal achievements here and there, but power sustained through the barrel of a gun has a short shelf life. What we are witnessing is not renewed strength, but a grievously wounded hegemon lashing out. The catastrophe of the Iran war makes the point plainly: the Trump doctrine can deliver only bloody turmoil – and an accelerating erosion of US power.