Since the end of the second world war, there has been a remarkable consensus within the US establishment about foreign policy. Republicans and Democrats alike have supported a global network of American-led alliances and security guarantees.
Leading figures in both parties — from John Kennedy to Ronald Reagan through to the Bushes and Clintons — agreed that it was in US interests to promote free-trade and democracy around the world.
Donald Trump has taken an axe to this Washington consensus. The US president’s departure from the established principles of American foreign policy is so radical that many of his critics dismiss his ideas as simply the product of a disordered mind. But that is a mistake. There is an emerging Trump doctrine that makes internal sense. There are four broad principles underpinning this approach.