Why do great powers disappear?

"Hard times create strong men; strong men create good times; good times create weak men; weak men create hard times," wrote Michael Hopf in his 2016 novel Those Who Remain.

Historians have wondered for centuries whether history is linear or, on the contrary, cyclical. Since ancient times, both have investigated the reasons for the rise and fall of great empires. The famous passage in which Scipio Aemilianus weeps after burning Carthage, Rome's eternal enemy, in 144 BC is famous. "Why are you crying?" Polybius asked him; "because sooner or later this will happen to my country." And so it happened... 590 years later.

The historian Ibn Khaldun, a Tunisian and son of Sevillians, was impressed in the 14th century by the magnificent ruins of the ancient Roman cities of North Africa and his comparison with his present-day counterparts. He secluded himself in a castle for a few years and wrote the Muqaddimah, a philosophy of history that explains the decline of empires when they lose their cohesion , making it easier for more technologically, militarily, and economically backward peoples to overthrow more "advanced" ones, as the barbarians did to the Western Roman Empire.

Recently, the well-known Swedish historian of ideas, Johan Norberg, has published a delightful book, Peak Human , in which he analyses the rise and fall of several empires: the Athenian empire of the 5th century BC, the Roman empire, the Abbasid Caliphate of the 8th century, Song Dynasty China (10th-13th century), Renaissance Italy, the Dutch Republic of the 17th century, and finally the present-day "Anglosphere" (a term that would encompass the USA, the UK, Canada, Australia and New Zealand).

According to Norberg, successful empires emerge from open borders, openness to innovative ideas, trade, and skilled immigration. "Our city is open to the world," Pericles said, honoring those who fell in battle against Sparta. From its Republican era (5th century BC), Rome welcomed elites from surrounding populations, an essential factor in the fabric of stable alliances that allowed it to dominate Italy and, later, "conquer the world in self-defense." The Baghdad of Harun al-Rashid, caliph of The Arabian Nights , was the most prosperous and cosmopolitan city in the world; and it was during the Song Dynasty that China generated important scientific advances (gunpowder, printing, paper money, compass, etc.) that allowed it to advance over the rest of the world. These processes of technological and commercial liberalization also explained the rise of Renaissance Italy (not a political empire in itself, but a cultural empire), the Netherlands' independence from Spain (a maritime and commercial empire), and the rise, first of the United Kingdom in the 18th and 19th centuries, and later of the United States in the 20th century. Although the author doesn't analyze it, I believe there are important parallels with the Spanish monarchy of the 16th and 17th centuries.

Why do empires fall? According to the author, when a great power suffers a significant setback, it tends to withdraw into itself, and this isolation accelerates its decline for the same reasons why its openness was key to its rise. Thus, the devastating wars unleashed by Sparta and its allies (the established power) against Athens and its allies (the emerging power) caused a progressive closure of Athens, a closure that led to its economic, military, and even moral decline. Something similar happened with the Roman Empire from the 3rd century onwards, which, after suffering devastating plagues and attacks on its borders, gradually closed in. It subsequently saw the Goths peacefully enter its territory in 376 AD and take Rome just a few years later in 410, thus materializing Scipio's terrible vision of a few centuries earlier. These "closures" also occurred among the Abbasids (as a consequence of the progressive revolts and splits of Islam), the Ming (after the Mongol conquest that put an end to the Song), the Italian Renaissance (foreign invasions from 1494), and the Dutch splendor, curtailed by the French invasion at the end of the 17th century.

The book doesn't analyze the current situation, but one wonders with amazement whether the current situation in the United States bears any parallels to that of other empires that, after reaching their peak, began their decline. The United States has built the greatest power in history thanks to the openness discussed by Norberg: a cocktail of openness to innovative ideas, immigration (a quarter of US patents are the work of skilled immigrants), and a marked openness to trade. Yet, a supposed "trade defeat" against China and other countries is leading the United States to limit its borders to trade via tariffs (the current tariff is 17%, compared, for example, to 2% in classical Athens), restrict immigration (skilled and unskilled), and close itself off to ideas through massive cuts in research and development funding, something that will result in thousands of layoffs of scientists, many of whom will emigrate to Europe in what could become the largest brain drain in history . Norberg also fails to reflect other "symptoms of decline," such as spending more on debt interest than on defense (the US has just done so), or Khaldun's lack of "cohesion," which, when projected onto the US, is chilling.

Einstein said, "The measure of intelligence is the ability to change." Empires have changed in unintelligent ways, history tells us. Let's hope that's not the case with the US.

Ignacio de la Torre is chief economist at Arcano Partners