Angela Merkel and Emmanuel Macron both came home from Washington empty-handed. Europeans should focus on stemming the tide of populism and stay united.

The visit was not even as bad Angela Merkel had feared in the darkest hours: no scandal, no harsh argument, not even a clumsy joke like the last time. During the press conference, the American president even congratulated the chancellor on her re-election.

Nevertheless, that was it.

Aside from a couple of nice words, Merkel was unable to bring anything home. The sad outcome of her journey is that Donald Trump is astoundingly unchanged. Not only does he tweet as if he were still in the middle of an election, he also continues to bend the facts so that they fit into his worldview. He knows no allies or partners, only deals and the will to get the maximum benefit for himself and the U.S.

Anyway, the hope that Trump will give up on tariffs against Europe and stick to the nuclear agreement with Iran is vague at best. Trump leaves everyone in the dark, and he enjoys the power he derives from uncertainty. “We'll see what happens” is one of his favorite sentences.

How do you handle someone like that? This week, we had the chance to observe two methods: Emmanuel Macron’s impulsive, if somewhat forced, friendliness and Angela Merkel’s Uckermark coldness.* As far as one can tell, neither approach was successful. Although Macron was greeted with great pageantry, he could not bring any tangible results home from Washington, just like Merkel, who was dismissed after a 20-minute conversation and a quick lunch.

This week’s lesson is that Trump is happy to hear flattery, but does not let it alter the course of his policies.

Therefore, the only hope left is that Trump can be swayed by what is the weak spot of any politician: his interests and voters. A trade war would destroy jobs in America as well, and who would profit from a new conflict in the Middle East?

It is therefore right that Europeans speak clearly, even bluntly, with Trump. Nothing disgusts dealmaker Trump more than weakness. However, Trump has proven enough times that he is willing and able to disregard the facts. In the worst-case scenario, Europe must be prepared to spend another three years dealing with Trump's madness in order to limit the damage.

Containment was once the strategy with which the U.S. attempted to limit the Kremlin's power and ambitions after the end of World War II. Now it is needed to stem the tide of populism and it will only work if the European Union stays united.

Trump is clearly trying to drive a wedge between EU countries; their interests diverge even on the issue of tariffs: France wants to safeguard its agricultural products; Germany is looking after its car industry. The American president knows that of course, and has also realized that he can appeal to Macron’s vanity with flattery. If Trump manages to drive Europe apart, he will have reached his goal. Or, in his own words, “Great success!”

*Editor’s note: Merkel is a native of the Uckermark region of Germany, northeast of Berlin.