Half a year into his presidency, Mr Trump’s foreign policy has five distinctive features. The Trumpian approach differs from that of his predecessors in type, not just degree, and other countries around the world need to be aware of the dissonance with past conduct.

First, Mr Trump is transactional, not institutional. He views foreign policy like a dealmaker and does not care whether the outcomes fit America’s traditional practice of building systems that advance its interests and values. As a negotiator, Mr Trump will be periodically confrontational. He can be impulsive. He welcomes creating uncertainty, which he believes builds leverage. Mr Trump’s ego plays an exceptionally large role and so do personal — and even family — relations. He is the first president in my experience who does not believe the office is larger than himself.

Second, Mr Trump’s domestic political interests will dominate his foreign policy. One wise American statesman suggested to me this spring that Mr Trump, like other presidents, wants to be successful, and therefore would move closer to mainstream policies. This assessment depends on how one defines success: I believe Mr Trump’s aim is a political realignment, which he thinks he can achieve by embracing and voicing the grievances of his voters.

Accordingly, he welcomes battles over trade, immigration and his wall with Mexico. Note as well that the president’s directive in the Middle East is to destroy the terrorists of Isis — obvious enemies that his backers can recognise. He has no plans to complement military action by creating forces or safe zones that can establish a rough power balance on the ground and resist Iranian expansion.

After being compelled to remain in Afghanistan when he wanted to withdraw, Mr Trump will redefine the battle as smashing terrorism in line with his supporters, even though he really will need to strengthen the Kabul government’s capacity to succeed.

Third, trade policy will reflect most explicitly Mr Trump’s dissonant outlook. He proudly embraced protectionism in his inaugural address, the first president since Herbert Hoover to make such a public stand. Take Mr Trump at his word. In order to signal a belligerent break with the past, he abandoned the Trans-Pacific Partnership, whose new rules and market openings would have benefited the US. Mr Trump and Wilbur Ross, commerce secretary, view bilateral trade deficits in the way businesspeople view negative net income: as losing. Therefore, countries that have large bilateral surpluses with the US — such as Mexico, South Korea and Germany — will draw presidential ire.

Adroit early visits by the leaders of China and Japan led them to hope they could avoid Mr Trump’s aim, but they are mistaken. The president’s problem will be that bilateral trade deficits are hard to modify through trade policies; to address them, the administration will most likely turn from rules for fair competition and openness toward managed outcomes, dictated market shares and requirements for national content. Watch the renegotiation of Nafta to learn how Mr Trump will try to translate political rhetoric into policy.

Fourth, Mr Trump is ambivalent about alliances. He believes that the US has been too generous and can no longer afford the 70-year old security system that America led in creating after the second world war. But the US alliance network has forged a resiliency through professional ties, planning, institutions and even the careers, customs and habits of the US military.