US President Donald Trump in the Oval Office. Credit:Evan Vucci The Jerusalem decision is an excellent case study of Trump's overall foreign policy. In recognising the contested city as Israel's capital, Trump was responding to domestic pressures from conservatives and evangelicals rather than following some grand strategy about world affairs. While he was not the first Republican candidate to promise to recognise Jerusalem as Israel's capital – George W. Bush did the same in 2000 – he was the first to overcome the constraints of foreign policy considerations, in large part because he has none. That may sound like an odd claim, given that Trump's campaign slogan, America First, was as much a foreign policy claim as a domestic one. It harked back to the days before World War II, when the US had pulled back from its international commitments and showed little interest in involving itself in world affairs. It was a stance that made sense after the folly of World War I and a decade of economic depression. Those same conditions – war-weariness and economic collapse – carried Trump into office, making him seem part of a longer historical tradition of something between nationalism and realism.

Trump's strategy with North Korea has nicknamed Kim Jong-un "Rocket Man". Credit:Wong Maye-E That same philosophy appears in the administration's recently released National Security Strategy, which he outlined in a speech last Monday. In that speech, Trump argued that his approach to the world was defined by competition and co-operation, an awareness of other great powers and a willingness to work with them when possible and compete with them as necessary. He labelled this strategy one of "principled realism", a phrase that suggested the importance of both restraint and values in foreign policy decision-making. A rally in front of the US embassy in Canberra to protest Donald Trump's Jerusalem ruling. Credit:Sitthixay Ditthavong Neither restraint nor values are hallmarks of the Trump administration, so it would be fair to ask whether this strategy really represents the forces governing foreign policy. And the evidence suggests that other forces are far more powerful, especially bellicosity, domestic concerns, and impulsivity.

Those are the defining features of, for instance, his approach to North Korea, which thus far has mostly consisted of threatening apocalyptic war and nicknaming Kim Jong-un "Rocket Man" rather than the hard work of diplomacy. Behind the scenes, the departure from principled realism is even more pronounced. Though on the campaign trail Trump regularly bashed the Bush administration for lying about weapons of mass destruction and leading the US into a dumb war, his administration, led by National Security Adviser H.R. McMaster, is currently building its own case for pre-emptive war against North Korea. There are many ways to describe the idea of launching such action against North Korea over weapons of mass destruction. "Principled realism" is not one of them. The same impulses feeding Trump's North Korea policy came into play with his Jerusalem decision. Domestic politics and bellicosity loom large: Trump wants to look tough and do the things other politicians wouldn't do. But Trump's low tolerance for hard work matters, too. Pronouncements are the easiest part of the presidency. Say the thing, and it is done. Thus Trump has signed countless executive orders but little legislation. Thus he has cluttered up Twitter but made barely a dent in most of his long-term policy promises. And when it comes to the Middle East, it is far easier to recognise Jerusalem than work on his other goal for the region: peace talks.

Indeed, he has sacrificed this other, bigger goal for the easy win. Because while past presidents have indicated that they strongly feel Jerusalem should be recognised as Israel's capital, they have repeatedly refrained from doing so because they understood that the decision was a vital part of negotiations between Israel and the Palestinian Authority. By siding with Israel, Trump has sacrificed more than just a crucial bargaining chip. He has sacrificed America's standing as a mediator in the peace process, threatening to bring more instability to the region. There are serious debates to be had about America's role in the world. After the disastrous Bush interventions, Barack Obama attempted a more restrained approach to world affairs and found it difficult to avoid entanglements and restore stability. Those shortcomings suggested the need for a robust discussion of what sort of principles should guide American involvement going forward. With the Trump administration, the country has got not a set of principles but a set of impulses, ones that have made the world even less safe than it was when he took office. Nicole Hemmer is a Fairfax Media journalist based in the United States.