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We now are on the brink of a trade war between the United States and its allies. The Trump administration confirmed this week that it will impose tariffs on imported steel and aluminum from the European Union, Canada and Mexico. The measures were announced earlier in the year, but the United States's neighbors and the E.U. — all vital diplomatic partners — had been granted temporary waivers as negotiators sought a compromise that would reduce import levels and allay the White House's grievances over trade deficits.

But on Thursday, Secretary of Commerce Wilbur Ross made clear that the talks hadn't worked. Tariffs of 25 percent on steel and 10 percent on aluminum were expected to take effect at midnight.

The response was swift and scathing. The affected parties all vowed to slap their own retaliatory tariffs on American goods. "This is a bad day for world trade," declared Jean-Claude Juncker, the president of the European Commission. He announced that the E.U. would "introduce a settlement dispute with the World Trade Organization" and enact "counterbalancing measures."

The Mexican government said it would target U.S. exports of pork bellies, apples, cranberries, grapes, certain cheeses and various types of steel. Canada said it would slap dollar-for-dollar tariffs on a range of U.S. products, including whiskey and orange juice. And the European Union indicated it would levy taxes on about $7 billion worth of U.S. exports, including bourbon, Harley-Davidson motorcycles and jeans.

The White House received a significant amount of domestic flak, too. Both the steel industry and steelworkers' unions decried the tariffs. Other manufacturers were no less concerned: One study suggests that the tariffs could kill up to 40,000 jobs in the automobile industry alone.

Republican politicians, at least those still invested in defending free trade, panned the decision. “This is dumb. Europe, Canada, and Mexico are not China, and you don’t treat allies the same way you treat opponents,” said Sen. Ben Sasse (R-Neb.). “We’ve been down this road before — blanket protectionism is a big part of why America had a Great Depression. ‘Make America Great Again’ shouldn’t mean ‘Make America 1929 Again.'”

But that motto seems increasingly apt. “The president seems to be following through on his promises of putting America first, in a weird and harmful way,” said Paul Musgrave, a political scientist at the University of Massachusetts Amherst, to Vox. “Since the campaign, he has made clear that he views allies as takers and wants to renegotiate the post-World War II liberal trading order to put the screws on them. It’s a callous, extortionate view.”

The Trump administration forced through the measures by invoking national security, which gives the president more executive authority to impose these duties. By casting his transatlantic partners as potential threats, argued Ed Luce of the Financial Times, he's pandering to a nationalist base and "replacing a system of rules with political whim."

Luce goes on: "Launching a simultaneous trade war against America’s allies and adversaries conforms to no known international rules of logic. It will raise domestic prices, cut U.S. jobs and reduce America’s global influence." But this is no accidental project. Luce observed that Trump's chief trade negotiator, Robert E. Lighthizer, "has long nursed a grievance" against the WTO and will probably lock horns with its technocrats in the coming months — giving Trump another foreign clash upon which to grandstand.

For European officialdom, Trump's behavior is galling, but no longer surprising. German and French entreaties could neither salvage the nuclear deal with Iran nor dissuade Trump from pulling out of the Paris climate accords. Rather than giving NATO its traditional backing, Trump has mostly groused over European military budgets. And he has been a vocal activist against free trade, eager to be seen as the world leader standing against the tide of globalization.

So if Juncker complains that the tariffs are "protectionism, pure and simple," that won't bother the White House. But the damage done to the relationship with Europe may be real, far-reaching and possibly even self-defeating for Trump. If he wants to win his larger trade battle with China, he will need support from allies he's now making into enemies. Instead, he may be pushing Brussels closer to Beijing.

"Thursday’s action also is expected to complicate U.S. efforts to confront China over trade practices that the administration regards as unfair," my colleagues reported. "The E.U. shares many of Washington’s concerns about China’s efforts to acquire advanced technology through compulsory licensing practices, cybertheft and other measures. But European officials are increasingly irritated by Trump’s aggressive use of obscure provisions in U.S. trade laws against U.S. allies."

The rift comes at a difficult time. Political crises in Italy and Spain will test the strength of the continental bloc and the integrity of its single currency. Populist factions in various countries are challenging the liberal values that once grounded both the European project and the transatlantic alliance.

The White House is playing a key role in deepening that challenge, as well as the sense of crisis afflicting the West. It has found common cause with illiberal governments in Poland and Hungary that happen to be the bêtes noires of Brussels. Hungary's foreign minister, Peter Szijjarto, was in Washington this week, hailing growing business ties while mocking Western European leaders for their opposition to aspects of Trump's foreign policy. “Hungary will not join the European choir that has now made a hobby of criticizing the United States," said Szijjarto.

Meanwhile, America's traditional partners now find themselves in a strange place, forced to confront a friend as a foe.

"Americans remain our partners, our allies, and our friends. This is not about the American people," said Canadian Prime Minister Justin Trudeau, speaking almost in the same register as a U.S. diplomat engaging an authoritarian adversary. "We have to believe that at some point common sense will prevail, but we see no sign of that in this action today by the U.S. administration."

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