On September 2nd, 1987, Donald J Trump paid $94,801 to publish an open letter in the Washington Post, the New York Times and the Boston Globe. In the full-page adverts, Trump wrote: “The world is laughing at America’s politicians as we protect ships we don’t own, carrying oil we don’t need, destined for allies who won’t help. Over the years, the Japanese, unimpeded by the huge costs of defending themselves (as long as the United States will do it for free), have built a strong and vibrant economy with unprecedented surpluses.”

Trump’s letter, which went under the headline “There’s nothing wrong with America’s Foreign Defence Policy that a little backbone can’t cure” was written against the backdrop of the ongoing Iran-Iraq war. By the summer of 1987, the fight had reached such a boiling point that when Iran stepped up its attacks on Iraq, the US undertook the biggest naval convoy exercise since World War 11 to escort Kuwaiti tankers through the Gulf.

For Trump, this was a scandal. And his message to the US public that September was clear – the US had a bad deal from its allies. What’s more, these bad deals were to blame for American economic weakness. As Trump asked in his letter: “Why are these nations not paying the United States for the human lives and billions of dollars we are losing to protect their interests? Saudi Arabia, a country whose very existence is in the hands of the United States, last week refused to allow us to use their mine sweepers (which are, sadly, far more advanced than ours) to police the Gulf.”

On the same day that Trump published his letter, he went on Larry King’s CNN show, telling his audience that other countries “laugh at us behind our backs, they laugh at us because of our stupidity and [that of our] leaders.” If he was furious with America’s Arab allies, he was angrier still with US policy towards Japan, a country he claimed had kept its currency low in order to gain advantage; not unlike the scorn he is now heaping on China and Germany.

Indeed, the idiocy of past US presidents and their flawed foreign policy is a theme that Trump has been banging on about since the early 1980s. It’s just that no one has listened. But it’s there in all the speeches and interviews he has given over the last 40 years as historians Charlie Laderman and Brendan Simms show in a humdinger of a new ebook hot off the press, Donald Trump: The Making of a Worldview.

Laderman and Simms have trawled through all the speeches, books, articles and tweets that Trump has poured out over the last four decades and the picture that emerges from their reportage is crystal clear too. Any assumption that his foreign policy views are impulsive and inconsistent – or made up on the hoof on the campaign trail to lure rustbelt and redneck voters – is false. Furthermore, the idea that the Trump of today is a fool or a buffoon who has improvised his way to becoming Commander in Chief of the most powerful nation on the planet is not only nonsense but dangerous. As they say: “Don’t say he didn’t warn you.”

What Laderman and Simms illustrate in the most fabulous detail is how the real-estate developer has held – in the main – a consistent position on America’s place in the world and on economic trade ever since he made his first public statement on foreign policy dating back to an NBC interview in 1980. And, give or take a few wobbles, Trump has carried on making these same points right on until he climbed to the White House. Why no one has spotted this consistency before is extraordinary.

Listen to him on how the US is losing out in international trade in the early 1980s: “Free trade can be wonderful if you have smart people, but we have people that are stupid. We have people that aren’t smart”. In an interview with Oprah Winfrey in April 1988, he warns again about Japan and the Gulf oil states, saying: “They come over here, they sell their cars, their VCRs, they knock the hell out of our companies. And, hey, I have tremendous respect for the Japanese people. I mean, you can respect somebody that’s beaten the hell out of you. But they are beating the hell out of this country. Kuwait, they live like kings, the poorest person in Kuwait, they live like kings and yet they are not paying. We make it possible for them to sell their oil. Why aren’t they paying us 25% of what they are making? It’s a joke.”

Here is Trump again in an interview with Playboy in 1990: “People need ego, whole nations need ego. I think our country needs more ego, because it is being ripped off so badly by our so-called allies.” And if he ever became president, he said his first act would be to “throw a tax on every Mercedes-Benz rolling into this country.” (By the way, he also predicts President Gorbachev will be thrown to the wolves. )

There’s another early King interview, where he criticises America’s allies, including Nato and the Germans for “ripping off the US and laughing at us again” and accuses Japan and Saudi Arabia for distorting the market. And he’s consistently criticised US leaders for giving in to Mexico, to China on the environment and indeed, even though he was against intervening in Iraq, for leaving without taking any oil.

That’s enough of the teasers; you must get this perfectly timed book to read for yourself the raw meat of what he has said, and how at times he has shifted positions.

Yet the big question is whether Trump’s past comments are a pointer to future policy? Will he dare cut back from Nato or force the other Nato countries to cough up more? Will he drop sanctions against Putin, and work together with him to sort out the Middle East and take on China? Perhaps most pertinently, will he actively work to break-up the EU with his criticisms of Germany’s hegemony of Europe in this critical election year?

Or will Trump be forced to switch positions when faced with realpolitick? He’s already tasted blood this week as the first US soldier was flown back to America after the failed sortie in Yemen. Trump will not have liked the dead bodies or the failure, even though it was a raid planned by Obama’s regime months ago but which was held up because of moonlight.

As you would expect, the authors are far too smart to gamble with any predictions. Yet I suspect they believe Trump will try his damnedest to pursue his worldview as far as he can; leopards don’t change their spots or their big red ties. And they quote Henry Kissinger’s famous comment that, as there is little time for Presidents to learn on the job, they usually consume the intellectual capital they bring to the office. Anyone interested in what Trump might do tomorrow, let alone over the next few weeks, should read this gripping account of what is going on under that combover.

Donald Trump: The Making of a World View. Brendan Simms & Charlie Laderman, 2017. 

The US version is available here, and the UK version is available here

Brendan Simms is a Professor in History of European International Relations, at the University of Cambridge. Charlie Laderman is a Lecturer in International History at the War Studies Department, King’s College London