by Brian Fagan
Where Ginghis Khan excelled was not only in conquest, but in his realization that an empire—as distinguished from a kingdom—had to be based on stable government, efficient administration, prosperous trade between the steppes and the settled lands, and law and order. He turned the expanding Mongol domains into a huge empire linked by efficient communications and kept in order by veiled military threats and the savage reputation of his troops. It was Ginghis Khan who told his armies to conquer first, then plunder, not to conquer and plunder at the same time. Rebels and chiefs convicted of treason received brutal punishment. Sometimes they were rolled in carpets and trampled by horses. Or, like one Kurdish chieftain, they were bound, smeared with sheep grease, then left to starve and be consumed by maggots.
The Great Khan considered himself the instrument of divine punishment, but, in reality, his lightning conquests owed much not only to his leadership and charisma but also to the realities of medieval climate on the steppes and to a lifeway that depended on mobility and the unique anatomy of the horse. The rhythms of nomadic life danced to the oscillations of the desert pump that brought drought, heat waves, bitter cold, and floods. These rhythms developed deep in history, long before the four centuries of medieval warming descended on the steppes. But where Ginghis Khan showed genius was in trying to move his domains away from the tyranny of the horse and the desert pump. In this he, and his successors, at least partially succeeded.
THE NOMAD’S STAGE covered an enormous tract of varied terrain from the Danube in the west in an ever widening belt that became part of the central Asian steppes east of the Volga River. The horse country extended to the Great Wall of China, more than 4,350 miles (7,000 kilometers) to the east. Popular writers often paint the steppes as a huge, rolling grassland that extends for thousands of kilometers without change. In fact, the term “steppe” encompasses a staggering variety of different environments—forest steppe, which is relatively better watered and well wooded; open grassland; river valley; marshland; and mountain range.8 Marshes, endless forests, and open tundra marked the inhospitable northern boundaries of the steppe. To the south, grasslands and deserts run from the Nan Shan and Tien Shan mountains, the “Mountains of Heaven,” in the east, along the Oxus River and the Iranian plateau, then lap against the natural bastions of the Black Sea, the Carpathians, and the Danube. But the heart of the steppe has always been the pastures along the northern edge of the Tien Shan and the southern edge of the Altai. Since the time of the Scythians, more than fifteen hundred years ago, nomadic horsemen have galloped through the low passes between these mountain chains, out of Asia into Europe.
By any standards, the distances are enormous, unfolding amidst landscapes where people and their animals are diminished to tiny dots against land and sky. The medieval friar William of Rubreck, who came to the Mongolian court as a papal envoy in 1253–55 and visited one of Ginghis’s successors, Möngke, said that the steppes were “like the ocean sea,” vast, mostly uninhabited, and dangerous. To travel across such country is to be lost in the immensity of landscape, to be dwarfed to insignificance by the sheer scale of the terrain. The steppes diminish the individual. I remember once crossing the Kafue River Valley in central Africa, an utterly flat, seasonally inundated floodplain. We saw what appeared to be some trees in the distance; then they started to move. They were a herd of several thousand antelope. Ghingis Khan’s horsemen would have seemed like moving trees in the immensity of the steppes, but trees that brought danger, menace, and slaughter. The Great Khan is said to have told William of Rubreck that “just as the sun spreads its rays, so my power . . . is spread everywhere.”9
Locations mentioned in the text. Some minor places are omitted.
The continental climate of Eurasia is always harsh, with average temperatures falling from west to east. Flat topography, low rainfall, and frequent dry winds inhibit tree growth. Winters are eight months long, dry, often intensely cold, and windy. The endless winds redistribute the snow cover, such as it is. Summers are torrid; heat waves and droughts are commonplace. As you move eastward past the Urals, the temperatures drop even further, winter snow stays on the ground longer, and the climate is considerably drier. Throughout the steppe, plants grow deep root systems in response to the aridity, while most smaller animals live underground. In ancient times, wild horses and asses, also saiga antelope, moved across the steppe in herds of up to a thousand. They did no damage to the bunched grasses of the steppe, which thrive under moderate grazing. But overgraze the pasture, especially when the soil is wet in spring, and rapid moisture loss decimates the graze.10
The steppes were a demanding homeland, even for the most expert herder. Ginghis Khan could sweep aside armies and overthrow kings, but he could not control the environmental realities of the steppes or the limitations of the horses that powered his armies.
A.D. 1100. The bitterly cold north wind of spring lashes the horsemen’s faces as they huddle in their saddles, leaning into the gloom. Their compact horses trot steadily, oblivious to the chill, following a barely discernible path through the shallow valley. Beyond lie the endless reaches of arid grassland, where a man can get lost in hours with no landmarks to guide him. It is early in the year to be on the move, but the men know that survival depends on their scouting journey. They have moved north from their snug winter quarters, traveling light through the winding valley where they and their ancestors have grazed their herds for longer than they can remember. As they ride, their eyes are never still, scanning the horizon for other, perhaps hostile riders, looking for patches of good grazing and signs that rain has fallen as the snows melted. In a few days, they will ride south with the wind on their backs, armed with vital intelligence of the staples of life on the steppes—grazing grass and water. Back in winter quarters, the khan and his advisers will rely on their observations to time the band’s move northward to summer pastures.
To the Mongols, the horse was everything—meat, milk, cheese, yogurt, even a source of alcohol in the form of fermented mares’ milk, koumiss. Horses were wealth, prestige, a potent military weapon, and, above all, a source of freedom and mobility. By the time of the Great Khan, the compact, sturdy Mongolian steed had been an integral part of steppe life for at least 4,500 years.
Horses were domesticated in about 3500 B.C., much later than cattle, goats, and sheep, on the margins of the steppes and probably in several locales: in the Black Sea region; perhaps also in the Altai Mountains, which are still archaeologically little known.11 Horses were much better adapted than other domesticated animals to intense cold and deep snow, and had been since the Ice Age, when they were a favorite quarry of tiny numbers of hunters on the plains. Between about 3300 and 3100 B.C., a colder, drier climatic cycle (which coincided with severe drought in Mesopotamia) led to much wider domestication of horses, which soon became central to human life on the steppe and changed history.
Horse riding was a revolutionary, if logical, shift in human transportation. It cut travel time across the steppe, allowing people to exploit widely scattered food resources, increasing territorial boundaries by a factor of five and making a mockery of earlier constraints. On the steppes, food resources could be quite rich in certain areas, such as major river valleys, but vast stretches of poor, sometimes hostile territory separated the areas of abundance. Anyone who could cover these distances relatively rapidly could survive on the steppe, and the entire shape of society changed as a result. Now one could transport large quantities of food and other goods with ease, especially when horses were combined with oxcarts. Wealth would be measured at least in part in horses; interdependency on neighbors and on settled farmers would increase, because horses were a desirable commodity thanks to which trading over long distances became much easier. Above all, mounted raiders could strike across long distances at their enemies and then retreat safely from pursuers on foot. By Ginghis Khan’s time, looting, raiding, and warfare had been an integral part of plains life for thousands of years. His remote precursors, the Scythians, were
the archetypal “barbarians” lurking to the north of the civilized classical world.12 The Greek historian Herodotus wrote of their savage warfare and described how they would scalp their enemies, turning their skulls into drinking vessels, which they set in gold and hung from their belts.13 When attacked, they would simply melt away into the vastness of the steppe.
The Scythians have been called the world’s best light cavalry. It was these master horsemen who introduced horses to temperate Europe. Their successors, the Sarmatians, who broke their domination in the fourth century B.C., are said to have invented the iron stirrup, which allowed them to carry long lances while in the saddle and to push their enemies off their horses.
The steppe nomads could never settle in one place, for to do so would invite disaster from overgrazing. They lived off their herds and their horses; sometimes they planted grain at a convenient locale, then left it unattended and returned months later to harvest the crop. But they also engaged in an intricate gavotte with the climatic pendulum because of their vulnerable mounts.14
Horses brought mobility, but they could also be a serious liability because of their digestive inefficiency. Cattle are efficient eaters in the sense that they excrete as little as 25 percent of the protein they consume. This means that they can eat dried-out, low-protein grass and still survive. Horses digest as little as 25 percent of the protein they consume; the rest, they excrete. Both use what one can call fermentation vats to convert plant protein into energy. The cow’s vat, the rumen, lies at a point in the body where food has not yet been digested. Here, bacterial action breaks down plant protein, much of it locked in the cell walls of the plant. The freshly broken-down protein passes into the duodenum, where it is broken down still further into amino acids. From there, the protein passes into the small intestine; here it is absorbed into the bloodstream and used for important purposes such as building muscles and nourishing fetuses. The horse’s rumen lies in the hind gut, in a position where the food has already passed through the duodenum and small intestine. So the horse produces small quantities of amino acids and does not absorb large quantities of protein through the intestine walls. Plant protein is broken down by bacterial action in an effectively useless location and becomes nitrogen-rich protein that benefits the soil, not the animal.
Normally, graze is so plentiful on the steppes that neither cattle nor horses need to retain all the plant protein they eat. But in times of drought, plant protein is in short supply. Living grass has about 15 percent protein; dead, only 4 percent. When dry conditions kill fresh grass, protein retention becomes all-important. Cattle retain three times more protein than horses do.
Horses had greater use in terms of military strategy and load carrying, but even one cold winter or an acute summer drought could kill dozens of beasts, especially when deep snow covered the ground or when winter feed ran short. Mares were unable to suckle their young; starving animals would start dying a few months later, with the drought destroying not only breeding stock but a vital source of milk, cheese, and yogurt.15 The nomads were forced to eat their dead horses. If the dry cycle lasted two or three years, the effects would be even more disastrous. Unable to find food, deprived of their horses, and incapable of defending themselves or raiding, they had no option but to join other groups, starve to death, or move. In some years, thousands of horses would perish. There was only one solution: move to better grazing. This usually lay to the south, on the margins of—or often on—lands settled by farmers.16
The gavotte between nomads and drought began long before Ginghis Khan and persists to this day. In it may lie one of the reasons why the Great Khan’s hordes burst on an unprepared and unsuspecting world eight centuries ago.
THE STEPPES ARE a vast blank with respect to climatic study: instrument observations, even today, are few and far between. By the same token, historical records from medieval times are a precious rarity, and even those tell us little about climatic events. Russian climatologists have cataloged extreme climatic events such as major droughts in Eurasia since the early eleventh century, tracing cycles of exceptional warm and cold over thirty-year periods. They’ve linked these cycles with thirty-year temperature and rainfall records derived from local proxy data such as tree rings and hydrological information. The resulting temperature curves speak of a four-century warm cycle beginning about A.D. 850, with mild winters and dry summers, which coincides with warmer conditions in western Europe. Not that the climate was always benign. The Chronicle of Novgorod tells of catastrophic autumn rains in 1143 and 1145 that destroyed the harvest and caused hunger. The chroniclers also tell us that there were seventeen years of climate-induced famine during the early thirteenth century, culminating in a drought-induced famine in 1215 that forced the city’s inhabitants to eat bark and sell their children into slavery. In 1230, another drought brought more suffering: “Some of the common people killed the living and ate them, others cut up dead flesh and corpses and ate them, others ate dogs and cats. . . . Some fed on moss, snails, pine bark, lime and elm leaves and whatever each could think of.”17 These disasters came at the height of well-documented warmer times in western Europe, when Norse ships still sailed to Iceland and Greenland and brought timber from Labrador. During the same period, the Slavs settled the coast of the Russian Arctic as far north as Novaya Zemlya, before the Little Ice Age descended.
The Novgorod chroniclers tell us that the climate of Eurasia’s warmer centuries was never static; serious droughts and cold winters alternated with periods of quieter, more benign conditions, such as those of the early fourteenth century. Since the Ice Age, the North Atlantic Oscillation and its seesaw of atmospheric pressure between the Azores and Iceland have governed western European climate. (For the North Atlantic Oscillation, see sidebar.) High pressure over the Azores and low pressure over Iceland bring persistent westerly winds and mild winters. But when high pressure builds over Iceland and Scandinavia, winter temperatures plummet both in the west and on the steppes. Central Asia is remote from the moderating influences of the Atlantic and Pacific; continental weather systems bring dramatic changes in temperature and rainfall, altering the environment of the plains within days. Even a slightly late spring or a few weeks of summer drought can devastate a year’s pasture. The records of the Novgorod chroniclers do not, of course, apply to the steppes, but we can be certain that the pattern of cycles of colder, wetter, and warmer and drier conditions applied over much of Eurasia.
The North Atlantic Oscillation
The North Atlantic Oscillation (NAO) is an irregular seesaw of changing atmospheric pressure between a persistent high over the Azores Islands in the Atlantic and a low that lingers over Iceland. The swings of the NAO are part of the complex atmospheric-ocean dynamic of the North Atlantic, which is still little understood. But the NAO is of critical importance, for it affects the position and strength of the North Atlantic storm track, which brings rain to Europe and parts of Eurasia. When low pressure persists over Iceland and high pressure builds off Portugal and the Azores, westerly winds persist over the North Atlantic, winter storms are strong, rainfall is plentiful in northern Europe, and winter temperatures are mild. Reverse the index from its “high” mode to “low,” when pressure is high in the north and low in the south, and Europe suffers under much colder winter temperatures while the westerlies weaken. Bitterly cold air flows south and west from the North Pole and Siberia. No one has yet succeeded in predicting the swings of the NAO, which can endure in the “high” or “low” mode for seven years or more, even for decades, but is sometimes subject to rapid shifts.
Another pressure gradient also affects European winters. In extreme “low” modes, persistent high-pressure systems form between Greenland and Scandinavia. Temperatures then are higher than average in Greenland and much lower than normal in both northern Europe and eastern North America. When the pressure over Greenland is lower than in Europe, the temperatures are reversed, and European winters are milder. Such a “Greenland low” may have persisted during the
warm centuries.
The behavior of the NAO depends on many complex factors, among them sea surface temperatures in the Atlantic, the mild waters of the Gulf Stream, and the powerful downwelling off southern Greenland that causes vast quantities of heavier, salt-laden water from the Gulf Stream to sink far below the ocean’s surface to fuel the ocean conveyor belt that circulates water through the world’s seas. There are clearly links between the NAO and the complex gyrations of the Southern Oscillation in the Pacific (see chapter 9), which generates El Niños and La Niñas, but they are still poorly defined.