Donald Trump claims this tariff gut-punch at his three largest trading partners is just a matter of common sense.
They in turn are imploring him to see reason, with Mexico and China calling for dialogue and cooperation.
Follow live updates: Trump ignites trade war
Canada's prime minister Justin Trudeau said on Saturday night - as he announced a reciprocal 25% tariff on $106bn worth of American goods - that the last time he had spoken directly with the US president was at Mar-a-Lago before the inauguration.
Much good that visit did him.
President Trump is defying the wisdom of decades that free trade encourages growth and prosperity in an interconnected global economy.
He is intent on rebalancing trade deficits, bringing manufacturing home and encouraging foreign investors to set up shop in the US.
His justification for tariffs is that they will force Mexico, China and Canada to halt the influx of fentanyl, its precursor chemicals and illegal migrants into the US.
Mexico is already working hard on both measures.
One of the few areas of diplomatic engagement with China over recent years has been the resumption of cooperation on counter-narcotics.
And as the Canadian prime minister said yesterday, only 1% of illegal fentanyl or illegal immigration crosses into the US via that northern border, and Canada is taking additional measures to reduce that further.
It is surely just a pretext.
Perhaps most alarming to any believer in the sovereignty of nations is the thought that President Trump really means it when he says "Canada should become our cherished 51st state".
He does not seem to be relenting on his threats against Greenland, after a testy conversation with Denmark's prime minister where he refused to back down on his demands on the territory.
Read more:
Why has Trump targeted Mexico and Canada?
How Donald Trump's tariffs could impact consumers
His secretary of state, Marco Rubio, is currently in Panama - where Trump has threatened to take the Panama Canal by force.
Break Canada's economy and this expansionist US president may believe he can bend their will.
Canada has more than just a trade war on its hands.
(c) Sky News 2025: Breaking economies could be just the first step for expansionist Trump
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