Carl Bildt is a former prime minister of Sweden and a contributing columnist for The Post.

It is only with effort that the leaders of Europe have managed to compose themselves after the U.S. election, torn between pure shock over the result and the necessity of preserving what can be preserved of the West and the Atlantic relationship.

If you listen to what Donald Trump has been saying during and before his campaign, this is the end of the West as we know it.

For more than half a century, this story of phenomenal success has been built on a commitment to freedom and democracy, free trade, solid alliances and reliable friendships.

But all of this has been either attacked or questioned by Trump. And no part of the success of the West has been more important than the success of Europe under the protection of and in a strong relationship with the United States.

Nigel Farage, the longtime leader of the United Kingdom Independence Party, arrived at Trump Tower on Nov. 12. (The Washington Post)

We should not forget that this has been profoundly in the interest of the United States as well. Twice in the past century it was dragged into wars as Europe plunged into acrimony and conflict. A peaceful, free and prosperous Europe has been a key strategic U.S. interest.

There has been a recognition that this aim is best furthered by the process of European integration centered on the European Union. A Europe that starts fracturing will be a less stable and, in the longer perspective, also a more dangerous Europe.

When Trump receives the jubilant British anti-Europe campaigner Nigel Farage before seeing other foreign politicians, he is sending the worst possible signal to Europe. By design or by default, he transmits a signal of support to those dark forces in various countries trying to undo what generations of U.S. and European statesmen have worked to achieve.

But the list of European concerns certainly doesn’t end there. It also includes his talk of abrogating the Paris global climate agreement, undermining the Iran deal, questioning important free-trade agreements — signature achievements and goals of the past few years that are suddenly up in the air. That there is deep apprehension around the capitals of Europe is hardly surprising.

Now the raw populism of the campaign will have to be turned into U.S. policy, and E.U. leaders will naturally be keen to see if this process will moderate some or all of these campaign promises. Appointments will be very closely watched.

And then there must be direct talks.

In April 2009, a newly elected President Obama came to a NATO summit in Strasbourg, France, and a special E.U.-U.S. summit in Prague before proceeding to an important speech in Ankara, Turkey. It was a jubilant new start for transtlantic links.

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Now there will be a new start of a very different sort.

European Council President Donald Tusk has invited Trump to a special E.U.-U.S. summit; there is the G20 meeting in Germany in late spring, and an extra NATO summit looks to be necessary as well. But it is very much an open question whether the air will have cleared sufficiently on the core issues of concern before such a meeting..

Security issues are bound to loom large. While Trump seems to have a benevolent view of Russia, he simultaneously is a hawk on defense spending in Europe.

Defense spending is on the increase in key parts of Europe, with most countries in the north and east having reached or aiming at 2 percent of gross domestic product. But it is how these sums are actually spent that matters, and it is here that both NATO and the European Union must do better.

And when it is often said that the United States accounts for 70 percent of the defense spending of the NATO countries, we should not forget that U.S. spending is global, with the explicit aim to have 60 percent of its air and naval forces in the Asia-Pacific region.

According to Vladimir Putin, there is now an agreement with the president-elect to start “active joint efforts” to normalize relations with Russia. Well, Europe certainly has nothing against good relations with Russia, but they have to be based on rolling back aggression against Ukraine, ceasing silent cyber-operations and respecting the rules agreed upon between nations.

If the United States starts to waver on these issues and caves in on them to the Kremlin, it will undoubtedly encourage a process of destabilization that is most unlikely to be limited to Europe. There might well be other powers that would be tempted by the American president suddenly tolerating smash-and-grab raids of the sort Putin has been doing.

There seems to be more geoeconomics than geopolitics in Trump’s thinking. It’s a question of making good business deals. If so, he should see the imperative of trade deals on the free-trade terms of the West, rather than allow a world dominated by the rules-free mercantilist approach of a China that will always give priority to its own gains. A transtlantic agreement would be of the utmost importance in this respect.

Henry Kissinger noted shortly before the election that “for the first time since the end of the Second World War, the future relationship of America to the world is not fully settled.” From the European point of view, that is a big understatement.