The European Union owes its origins to a trade agreement that involved coal and steel.
At its very heart is a belief that free trade between partners is a fundamentally good thing.
Nothing is more certain to upset policymakers in Brussels than the spectre of swingeing tariffs.
They saw this coming, of course. Leaders in both Paris and Berlin already made it clear that the EU was ready to respond, while bemoaning the whole thing.
On Tuesday, European Union chief Ursula von der Leyen vowed to retaliate against US President Donald Trump imposing tariffs on steel and aluminium.
“The EU will act to safeguard its economic interests,” Ms von der Leyen said in a statement.
“Tariffs are taxes – bad for business, worse for consumers,” she said. “Unjustified tariffs on the EU will not go unanswered – they will trigger firm and proportionate countermeasures.”
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Talk to diplomats across Europe and they’ll almost all tell you the same thing – that nobody wins from a trade war.
But beyond the anger and diplomatic fret, there is something else that could happen now, and strain relations with Washington even more.
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European leaders, with a few exceptions, are nowhere near to adopting the same protectionist viewpoint as President Trump.
That means that, if they think American markets are being closed off to them, then they will look for new places to sell goods.
And that is likely to lead in three directions.
Firstly China, which has always been seen as a less palatable and less reliable partner than America .
Now, that judgment is likely to be revised.
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Secondly, they will look at India, where a comprehensive trade agreement remains outstanding, despite growing bilateral trade.
And, thirdly, the EU will look at South America, another growing market.
And that wouldn’t just affect trade. If Europe develops closer economic relations with China, India, Brazil and others, then that’s bound to affect a welter of other geopolitical deals – exactly the sort of things that annoy and worry American presidents.
The consequence of American tariffs could see European nations forging new, and even unlikely partnerships, just as the old transatlantic friendship comes under strain.
