When it was first published in 1987, your magnum opus, The Rise and Fall of the Great Powers, made the central argument that a great power’s relative military and strategic position is inextricably linked to its productive and economic power. Given that, and drawing on your analysis of global geopolitics since then, who do you think will be the great powers by the middle of the 21st century?

I was intrigued by a future chart projection of the share of world total economic output by the year 2050, which would see three very large economies at the top of the pile, namely, the United States, the People’s Republic of China, and, because of a vastly higher rate of growth between the 2000s and 2050, India.

Now those three countries, the US, China and India, would have GDPs approximately six to eight times bigger than any of the ones directly beneath them – the middle-ranking powers such as Japan, Britain, Russia, and France. That would be the rough and ready order of the world in the year 2050. So the world of the nation states and national economies has not altered, just the nation states. And those three, if they wanted to, in total defence spending, would be way above anyone else.

A note of caution, however. In the meantime, epic things have happened in Washington, DC. We have an authoritarian powerbroker and deal maker in the Oval Office, an impulsive, I would say unscrupulous, president who makes things a little bit more complicated. I think we have a calculating leadership in Beijing, just watching to see how far Washington on the one hand and Moscow on the other, might stumble. I think that those leaders in Beijing do believe that they are in or entering this new tripolar world, along with India. It is a world in which they have to move very carefully and slowly, but from which they might be the beneficiaries.

You are a naval historian. Where do you see naval power within this bigger geopolitical picture? You wrote many years ago about how shipbuilding in East Asia, particularly in China, has been taking place on a remarkable scale. The significance of this wasn’t properly appreciated by many at the time, certainly not in Europe.

The first 20 years of the 21^st century involved a great explosion in world overseas commerce, with particular growth coming out of the exporting states of a new Asian economy. First, it was Japan, then it was the East Asian tigers, Korea and Taiwan, for example, increasing their productivity and exports. And then it was the enormous growth in exports from China. All were indicators of the shifts and the power balances that can also be seen in the changes in these countries’ shares of seaborne trade.

I have just come back from a visit to my native Tyneside [in the north-east of England]. I went to the shipbuilding towns of Wallsend and Jarrow, where, even 35 years ago, the air was grimy with the output of shipbuilding and coal. Nowadays, if you go to the reaches of the lower river Tyne, the epicentre of this industry, there are green grassy groves. There are skylarks overhead. I read that there are actually salmon rushing up the Tyne to spawn and then return. Yet this was one of the great epicentres of the Industrial Revolution. In 200 years, we have seen the story of Tyneside’s rise and transformation into an industrial centre of the world, and then deindustrialisation because shipbuilding moved to the East.

There may be some products made in the City of London: intellectual products, investment product, but it is not hard-nosed engineering and ship building, like the works of Vickers-Armstrongs. I’m affected by that background. This is not just me being romantic, it’s a developed hunch that measurements of power that are merely statistical, don’t have any hard punch to them and may turn out to be ephemeral. Shipbuilding is real.

Are we seeing a shift in the nature, the essence of geopolitics, as it moves away from the West?

If you look back at the great powers of the 19th century, and much of the 20th, they were largely European, geographically close together, rubbing up against one another. But, if my thesis of a new tripolar world is correct, how much will the US, China and India be militarily interested in the world far beyond their borders? Because one of the things that has been expected of great powers is that they take an interest in the generality of world problems. They have views on the Middle East, for example.

But China doesn’t have explicit views on the Middle East. India doesn’t have particular views on the Middle East. Both of them would probably rather not get involved. Beyond Taiwan, what are China’s interests? One might even say this is about the US at the moment, despite the bluster about Canada and Greenland. Great power, what’s it for? It just gives you trouble and you get involved in problems that don’t really interest you.

The US, China and India have plenty of space compared to say, France and Germany, with their competing historical demands over Alsace Lorraine, or Germany and Russia eyeing opportunities at the Polish border before the outbreak of war in 1914.

In the new tripolar world – with the US, China and India to the fore – there is enough room, enough space, and each of them have their well-defined areas of interest. There’s no need for them to stand on each other’s toes. It’s not one in which you’re so close together that you knock against each other. The nuclear threat posed by each of these nations might also cause them to be cautious.

So if you’ve got three powers, each with enough space, and an apprehensive approach to war, then maybe you can tolerate this 21^st-century world of three great nations at the top.

Does culture matter in this new world? 

There are always cultural factors that are very important and whose importance lies beyond the reach of hard, quantifiable statistics. We can’t measure them very well, if at all, but we do know that they’re there.

When I go to Delhi, I see a pretty antagonistic, large nation state which has not abandoned the idea that the use of force from time to time to advance or to protect Indian interests is perfectly legitimate. They are rather suspicious of being preached to about the non-use of force, especially by Europeans, given their colonial past. India is rather sensitive about where it is in the pecking order because it believes that it has a chance of getting closer to the top each year or at least each decade. And therefore, I see India imitating China closely in its rise.

You can point to specific cultural differences between them: one is a democratic system and one is definitely not a democratic system. Nonetheless, in their attitude to world affairs and hard power politics, I don’t see a big difference there and I think they will act and react in rather similar ways.

What currency do you think GDP will be measured in in 2050? 

Looking at lead currencies is another way of understanding how the world is or how the world may be going. The dollar is remarkably persistent, and it assists US power. There was a time 20 years ago when I saw it as a possible Achilles heel, that other countries might wish to trade heavily against the dollar and try to drive down its international trading value, perhaps triggering a run against the dollar. But much of the world’s financial instruments are issued in dollars now; nothing gets close to it. Indeed, the dollar denomination of financial instruments may now be significantly higher than it was 25 or 35 years ago. The financial measurements of American power look really very large and uncontested.

And yet, while you might think there would be a sort of cheeriness about a situation with the US on top, there’s a lot of angst about, for example, how many 50-year-old aircraft carriers the US has, which are enormously costly and vulnerable to the super submarines of other powers in the future. And about the military application of AI. So American anxiety about the military side may coexist with a great deal of satisfaction about the continuing fiscal strength and position of the US.

How do you know when you are living in a watershed moment, one of those great shifts between historical epochs? 

I was always caught by a remark made by the distinguished historian, Zara Steiner, who contributed two outstanding volumes to the Oxford History of Modern Europe on interwar diplomacy. Volume One, The Lights that Failed, runs from 1919 to 1933. Then volume two, The Triumph of the Dark, goes from 1933 to 1939, with just a little appendix for the Second World War.

Zara spent a great deal of time working on that masterly two-volume project, and she got particularly interested in the fact that she had had to split her project across this watershed of 1933. She posed this question of how did you, or how could the observers of the time, know that they were in a pre-Second World War part of history rather than a post-First World War part, their previous reality. At the time, there were assumptions about never going to war again, and different sorts of assumptions; ones about the coming again of a new imperial journey, for instance.

Zara’s answer was that you never could know. They could not have known whether they were in a pre-Second World War period by 1933 as opposed to being still in a the latter stages of the post-First World War period.

Closer still, when did we know that we were no longer in the post-Cold War period? The answer would surely be when our mental attitude started to move to the thought that we are more likely to be in the years of the next big conflict, when you start to have a different view of world affairs, and especially whether you’re going to invest rather more in the insurance policy of your national military more than you did before. I think we can safely say we are there now.

I wonder whether we’re entering into what is essentially a post-Enlightenment world. If we look at the great power struggles over the last 400 years, they were largely European. Going back to the 30 Years War, it’s clear that it was, at least in part, a struggle over salvation. This belief in salvation was secularised during the Enlightenment and, with whatever levels of sincerity, the civilising mission of the imperial European nations, such as Britain and France.

Even during the Cold War, we could see competing Enlightenment ideas – liberal democracy versus a kind of millenarian communism. There was a continuity there, whereas suddenly, if my thesis is correct, we’ve entered a post-Enlightenment world. What does this mean for Europe as the font of the Enlightenment? You could even argue that the European Union is the last Enlightenment project, but is it now just out of time? When I go to places like the World Economic Forum at Davos and I talk about great power projections, Europe is not in the story because there are now – and will be, if I am correct – at least three big muscular, selfish, antagonistic nations, all of which are non-European nations, in the US, China and India.

There is much unease among the Davos elite, because the World Economic Forum is almost like a last flurry of the Enlightenment, and especially its preoccupation with the economic dimension of order and its understanding and need for things to be measured, chiefly in terms of interconnected trade and investment flows and a nicely orchestrated exchange rate.

Yet that may not be the world to come. The future will be more of a narrow jostling between three big powers, with the rest carving out their place in the spaces in between. A large amount of a discourse on the need for Europe to stand together and be united is driven not just by a vision of Enlightenment progress, turning swords into ploughshares. It is also driven by the anxiety that Europe could be swept off the table of world affairs.