A large proportion of the world’s top tourist destinations are the remains of dead empires. A week of sightseeing with my younger children in Italy reminded me of this. The city of Rome was the capital of an empire that at its height stretched from Britannia to Babylonia. The city of Venice once ruled a realm that extended across what are now Albania, Croatia, Cyprus, Greece, Montenegro and Slovenia.

To walk among the monuments of the most Serene City and the Eternal City is at once inspiring and melancholy. Like Edward Gibbon, “I sat musing amid the ruins of the Capitol” — but musing about the decline and fall of other empires.

My grandparents and parents witnessed the decline and fall of the British Empire, but not before it had helped polish off the more ephemeral empires of Mussolini, Hitler and Hirohito. I experienced the decline and fall of the Soviet empire built by Lenin and Stalin. There are those who subscribe to the delusion that the age of empires is over. But all history is the history of empires.

The world today is dominated by two empires: the US, which originated in the British colonization of North America, and the ethnic-Han-dominated Middle Kingdom we call the People’s Republic of China. But a number of former empires continue to play disproportionate roles in world politics: The Russian empire limps on in the guise of the Russian Federation; the Persian empire is now the Islamic Republic of Iran; one might say the Holy Roman Empire has been reincarnated in the form of the European Union, at once extensive, German-centered and weak.

It is not civilizations that clash, but empires. Indeed, it is often border clashes that define their extents. As a schoolboy, I was taught the world wars as if they had been contests between European nation states. Only later did I see that they were struggles between empires. That was why they were global and not just European conflicts.

More recently, I saw that the term “world war” was a kind of optical illusion. What my paternal grandfather’s Victory Medal called “The Great War for Civilisation, 1914-1919” was really many conflicts: Austria’s against Serbia; Germany’s against Russia and its ally France; Britain’s to preserve Belgian neutrality (the one my grandad fought in); Britain’s and France’s to acquire Germany’s overseas colonies and to partition the Ottoman Empire between themselves.

My mother’s father served in the Royal Air Force in Burma and India between 1942 and 1945, returning home via the ruins of Germany. His was Britain’s imperial war to prevent its vast Asian empire from being taken over by the Japanese. But there were many other wars: Japan’s against China; Germany’s with the Soviet Union against the rest of Europe; then Germany’s with much of Europe against the Soviet Union; America’s war against all the Axis powers.

And after the world wars came the Cold War. We think of this as a struggle between two empires that pretended not to be empires: the US and the Soviet Union. But its conflict zones were largely defined by the process of decolonization, as the European empires disintegrated.

Like the world wars, the Cold War was an agglomeration of conflicts. What happened in Vietnam had little to do with what happened in the Middle East or southern Africa, aside from the fact that both superpowers had dogs in each fight — dogs that they armed and financed, enlarging and prolonging local conflicts by turning them into proxy wars.

These great conflicts were the dominant phenomena of the 20th century, transforming economic, social and political life almost everywhere. But in recent times, their importance has somewhat faded in most minds. It would not be too much to say that during the interwar era of 1991 to 2018 — in other words, the period between Cold War I and Cold War II — many economists and policymakers lost interest in war.

Because the wars of the interwar era were relatively small (Bosnia, Afghanistan, Iraq), more closely resembling colonial policing operations, we forgot that war is history’s most consistent driver of inflation, debt defaults — even famines.

Large-scale war is simultaneously destructive of productive capacity, disruptive of trade, and destabilizing of fiscal and monetary policies. Compare global battle deaths from interstate conflict with international inflation data from the Organization for Economic Co-operation and Development. You will see that behind the era of economic stability known as the Great Moderation, there was period of declining conflict that lasted from the early 1970s until the outbreak of the war in Ukraine. The coming of peace, like monetary policy, acted with lag.