Since the Chinese sage Sun Tzu authored The Art of War around 2,500 years ago, almost all writers on military affairs have asserted that a rapid rate of population growth is the sine qua non for a nation's decision to go to war.
More recently, this theory was elaborated by the Swiss mercenary, General Antoine-Henri Jomini, in a series of books that have been "must reads" in most military academies since the 19th century. Echoes of the same theory are present in On War, the military "bible" written by Carl von Clausewitz, the Prussian general and military historian, in the 19th century.
Thus, the Indo-European tribes left their ancestral homeland in Central Asia because they could no longer feed a rapidly growing population. Seeking more fertile land and pastures for their herds, they embarked on invasions to their west and south to find the resources they coveted.
The ancient Romans and Persians were also pushed towards conquest because of high birth rates that made the seizure of new lands a life-and-death necessity.
The Arab invasion of the Persian and Byzantine Empires in the Middle East and Asia Minor also came when the Arabian Peninsula could no longer feed its rising population. The same analysis has been applied to the Mongol invasion that brought hungry tribes from far away Mongolia to the heart of Europe and the Middle East.
Rapid population growth was also a key factor in pushing the British on a path of empire-building from the 16th century onwards. In fact, the ability to export large numbers of peoples to new lands is often cited as one of the key factors in empire-building since time immemorial.
Finally, the Nazis claimed that post-Weimar Germany needed to invade Europe in search of "Lebensraum" (living space) to secure agricultural and energy resources needed to be a big power.
Conquering nations always needed a high birth-rate to provide the fighters or the cannon-fodder every conqueror worth his salt needs. France's massive losses in the First World War prompted Georges Clemenceau, the wartime Prime Minister known as "The Tiger", to quip that "babies win wars, not generals".
But what if that old theory is no longer operative? In fact, what if the opposite is true; and that some nations are driven towards war because of declining populations?
Right now, three nations are actively or implicitly on a warpath against their neighbors: Russia, Communist China and the Islamic Republic in Iran. All three suffer from low birth rates, high death rates and a steadily growing number of old people.
In fact, in the past decade Russia's population fell from almost 147 million to 141 million in 2022.
A decade ago, Russia was the world's ninth-most populated country. It is slated to fall to number 22 within the current decade.
Russia's average birth-rate puts it at number 213, close to the bottom of world rankings. Worse still, the youngest portion of its population, aged from zero to 14, is the same as the portion of the oldest, aged 65 and over.
At the same time, the portion of gross domestic product (GDP) that the federation spends on the military is almost twice what is allocated to healthcare.
In other words, Russia could end up having lots of guns but not enough people to carry them. Things have gotten even worse since President Vladimir Putin launched his "Special Operation" against Ukraine. According to best estimates, during the last 12 months, almost one million Russians of fighting age have left the country to dodge the "voluntary draft" Putin has ordered.
Russia is also facing a growing labor shortage. In fact, without net immigration, mostly from Central Asia and Belarus, Russia may have faced even more biting shortages. Having enlisted over 100,000 men in the first year of the Ukraine war, Putin may need to import, not to say press-gang, people from neighboring countries.
A massive intake of Chinese "temporary workers" has helped, along with the addition of 100,000 "new citizens" from South Ossetia, part of Georgia that Putin annexed in 2008, and some 2.1 million Russophile Ukrainians shanghaied from Crimea, Donetsk and Luhansk.
China is facing a similar demographic perfect storm. For the first time in more than six decades, China has experienced an actual fall in its population, set to lose its ranking as the world's most populous nation to India. Worse still, China is experiencing a rising trend towards emigration, mostly to North America and Western Europe, especially among the young highly-educated strata of society.
The need to tackle the demographic deficit may be present, at least in filigree, in Beijing's increasingly belligerent discourse about Taiwan.
The Islamic Republic of Iran, too, is facing a demographic challenge that its leaders try hard to gauge.
Unlike Russia and China, Iran isn't yet facing an actual fall in its population, partly thanks to an inflow of Afghan refugees which, although slowing down in the past year or so, compensates for a growing outflow of young Iranians who immigrate to Western Europe and North America. A plan to settle over 100,000 "volunteers for martyrdom" from Afghanistan, Pakistan, Iraq and Lebanon, now stationed in Syria, in different parts of Iran is being finalized in Tehran.
However, the low birthrate -- less than one percent -- and the growing number of older citizens, reduces the number of men that the mullahs could send to war.
All profess different shades of hostility to the present world order, which they see as slanted in favor of "the West," led by the United States.
China, Russia and Iran spend almost twice as much on the military as they do on the health and well-being of their citizens. Their military expenditure as a percentage of GDP is more than twice the average of OECD countries, while their healthcare spending as a percentage of GDP is less than half of the OECD average.
The Ukraine war may show whether an authoritarian state with a declining and ageing population can win a war as did older authoritarian states with galloping demography -- in fact answering the question: Do babies still win wars?
Amir Taheri was the executive editor-in-chief of the daily Kayhan in Iran from 1972 to 1979. He has worked at or written for innumerable publications, published eleven books, and has been a columnist for Asharq Al-Awsat since 1987.
This article originally appeared in Asharq Al-Awsat and is reprinted by kind permission of the author.