Chapter Two
“They Are Monsters, Not Men”

ON A MAP, THE EURASIAN STEPPE LOOKS LIKE A TRAVELER’S PARADISE, but the steppe of the cartographers, the broad green crayon slash that sweeps effortlessly across the belly of the continent from Byelorussia to China, is a polite semifiction available only in spring, when the air is warm, the grass not yet knee-high, and the wind still fragrant with the smell of wildflowers. As Napoleon learned and Hitler after him, in winter waist-high snowfields transform the western steppe into an immense featureless sea that billows and swirls when the Arctic wind whips down from the Siberian tundra. The cartographer’s map also ignores the summer sun, which hangs so low over the treeless August plains, a traveler can almost reach up and touch it, and the incessant buzz of the mosquitoes, which grow almost as big as a man’s thumb on parts of the steppe and can leave a bite the size of a small tumor.

Farther east, on the Mongolian Plateau, where the steppe skirts the Gobi desert as it sweeps into China, cartographers often take note of the change in terrain with another polite semifiction—a splash of sandy color. Parts of the eastern steppe resemble a seabed baked dry by a billion years of sun. Between canyons of rust-colored cliff and sandy elevations more hill than mountain, low undulations of rocky ground flow to a limitless horizon like ocean swells, while overhead, above noisy flocks of circling carrion, the enormous sky oppresses with an infiniteness that crushes the soul. Even in high spring, the only two crops that grow in this part of the steppe are tufts of hard, spiky grass and the bones of the men and animals who failed to survive the winter snows.

InLa Practica della Mercata,Francesco Balducci Pegolotti attempted to ease the burdens of the medieval steppe traveler with reassurances—“the road you take from Tana to Peking is perfectly safe”; with sex tips—“the merchant who wishes to take a woman with him from Tana can do so”—and dos and don’ts—“do not try to save money on [a translator] . . . by taking a bad one.”* ButLa Practicawas a polite fiction, too. Upon leaving Caffa, a traveler could expect to spend eight to twelve months on the back of a Mongol pony or a jostling cart, to see nothing but horizon and prairie in every direction, and to feel no warmth at night except the body warmth of a traveling companion. As alien as the terrain were the fearsome Mongols who inhabited the Asian plains. “They [are] like beasts,” wrote one Westerner. “They live on wild roots and on meat pounded tender under the saddle . . . are ignorant of the use of the plow and of fixed habitation. . . . If you inquire . . . whence they come and where they were born, they cannot tell you.” William of Rubruck, a Flemish cleric who visited thirteenth-century Mongolia, described the Tartar women as “astonishingly fat,” with “hideously painted faces,” and the men as grotesques, with short, stocky bodies and “monstrously oversized heads.” Both sexes were also incredibly filthy; the Mongols refused to wash, believing it made God angry.

The French historian René Grousset has called the “discovery of Asia . . . as important to men of the Middle Ages as the discovery of America was to men of the Renaissance.” But it might be more accurate to describe the medieval discovery of Asia as a rediscovery. During Antiquity, news from the Orient would occasionally drift westward along the Silk Road, which wound through the necklace of desert between China and Arabia, or across the snowy passes of the Pamir Mountains in Central Asia, where representatives of Rome and China would meet to exchange goods. But from the seventh century onward, Europe became isolated on the western edge of Eurasia, a prisoner of its own disorder and collapse. To the extent that the reawakening West of the eleventh and twelfth centuries had a knowledge of the East, it was of the Middle East, and, more particularly, a thin strip of the coastal Middle East where Genoese and Venetian merchants were allowed to buy Asian goods from Arab middlemen at exorbitant markups. Beyond Arabia, everything faded into a myth wrapped in a fable. There were stories about strange Asian races like the Dog Men, who were said to have human bodies and canine faces, and the Headless Men, who were thought to have no heads at all; about Gog and Magog, who were believed to be related to the lost tribes of Israel; Prester John, a mysterious Christian King of the Orient; and the Garden of Eden, which was thought to be somewhere in India. But until the mid-thirteenth century, when the Mongols unified the steppe from Kiev to China, no one in the West was able to investigate any of these Eastern wonders firsthand.

The first Europeans to travel to Asia were clerics like John de Marignolli, a papal emissary, who pronounced the Tartar Great Khan “delighted, yea exceedingly delighted,” by the pope’s gifts, and John of Monte Corvino, who translated the New Testament into Mongol script, and whose long years in China aged him beyond his years. “I myself am grown old and grey, more with toil and trouble than with years,” John wrote after eleven years in the East. The group also included the rambunctious William, a Franciscan friar who endured every hardship of steppe travel, including the hardest of all, an alcoholic translator. From William, medieval Europe received its first description of Chinese script, of a potent Mongol liquor calledkoumiss,and of the Tebets, a Tibetan tribe whose members formerly ate their parents when they died but had given up the practice. William also was the first European to correctly identify the Caspian as a land-locked sea, not an ocean inlet, and—his proudest achievement—to participate in what may have been the first theological Super Bowl. On a May evening in 1254, in the Mongol capital of Karakorum on the edge of the Gobi desert, William strode into a crowded tent, and, in the presence of the Grand Khan himself, defended the Western concept of monotheism against atunis,a Buddhist priest.

“It is fools who say that there is only one God,” declared the wily Buddhist. “Are there not many great rulers on earth? . . . The same is true with God. . . . [T]here are ten Gods in Heaven and none is all-powerful.”

“So then,” replied William, “not one of your Gods is capable of rescuing you, inasmuch as [if you encounter a predicament] . . . the God has no power over, he will be unable to help you.”

On the basis of that exchange alone, William felt he had won the day, but, alas, the three Mongol judges who scored the debate disagreed and declared the Buddhist priest victor.

The second wave of European visitors were merchants, most Genoese or Venetian, enticed to the East by the opportunity to buy Asian goods at the source. No one knows for sure how many of these trader-travelers followed in the footsteps of Marco Polo, the daring young merchant’s son from Venice who crossed the steppe in the early 1270s; but by the early fourteenth century there were bustling Italian colonies in several Chinese cities, including Peking, and the two east-west trade routes open to Europeans buzzed with activity. Asia by sea could take up to two years—but oh! what sights the traveler saw along the way. The sea route could be picked up in Trebizond, a Greek colony in the Black Sea, or Tabriz, an Iranian city of thrusting minarets, so fabulously wealthy, a European visitor declared it “worth more to the Great Khan than his whole kingdom to the King of France.” From the Crimea and Iran, the route led down to the Port of Ormuz on the tip of the Persian Gulf, thence across the Indian Ocean to Quilon, an Indian kingdom where all the wonders of the seven seas seemed to have gathered under swaying palm trees. Quilon had lumbering elephants and chattering monkeys, local markets that smelled of pepper and cinnamon in the sultry heat, and a port crowded with huge, oceangoing Chinese ships whose sailors sang “la la la” as they rowed. The final stop on the journey was Hangchow, Venice of the East and one of the great wonders of the medieval world. A hundred miles around and guarded by twelve great gates, the city had blue-water canals, fire brigades, hospitals, and fine broad streets lined with houses upon whose doors were listed the names of every occupant. Along Hangchow’s canals, spanned by twelve thousand bridges and sailed by gaily colored boats, strolled the greatest wonder of all. This city has “the most beautiful women in the world,” declared a breathless Western visitor. In a nearby palace a Tartar khan was served his daily meals by five singing virgins.

However, because sea travel took so long, many Western merchants preferred the quicker overland route. In the Middle Ages there were several variations available, including the fabled Silk Road. But around 1300 a new route across the northern steppe began to gain favor. Travelers found the broad, flat terrain in the north easier on men, animals, and carts, but the new route had a significant disadvantage, though none of the newcomers realized it. It skirted the tarabagan colonies of Siberia, Mongolia, and northwest China.

Prized for its fur, the limpid-eyed, squirrellike tarabagan was—and still is—greatly feared on the steppe for its powers of contagion. InMemories of a Hunter in Siberia,A. K. Tasherkasoff, a nineteenth-century Russian writer, described how generations of nomad steppe hunters were weaned on stories of a mysterious tarabagan illness that could jump to humans foolish enough to trap sick animals (identifiable by a wobbly, staggering gait). According to steppe legend, the mysterious, highly contagious tarabagan illness was supposed to be caused by “small worms, invisible to the naked eye,” but in 1905, when the first infected animals were autopsied, the invisible worms turned out to be the plague bacillusYersina pestis,leading one scientist to compare the “tarabagan gardens” of the Asian plains to “a heap of embers where plague smolders continuously and from which sparks of infection may dart out . . . to set up conflagrations.”

More recent research on the tarabagan also has relevance for the Black Death. The tarabagan is a member of the marmot family, and, according to the Russian scientists who have studied the animals, the strain ofY. pestisthat circulates among marmots is the most virulent in the world. Besides extreme lethality, marmot plague, as the Russians call it, has another Black Death–like feature. It is the only form of the plague in rodents that is pneumotropic—that is, in tarabagan and other marmots, and only in them, plague has a tendency to spread to the lungs and become pneumonic. On the steppe, dead tarabagans are often found with a bloody froth around the nose and mouth—telltale signs of pneumonic infection.

American microbiologists tend to be skeptical about the Russian claims for marmot plague, but the Russians are so convinced of its virulence and lightning contagion that during the Cold War they bet their national defense on it. According to Wendy Orent, who has worked closely with many Russian scientists, whenever the Soviet Union drew up plans for a new plague weapon, Major General Nikolai Urakov, a leader of the USSR’s biological weapons program, would shout to his staff, “I only want one strain”—marmot plague.

Reconstructing any pathogen’s genetic history is necessarily an exercise in guesswork, but like the Black Death,Y. pestisseems to have originated on the steppe of Central Asia. Microbiologist Robert Brubaker thinks the big bang inY. pestis’s life may have been the end of the last Ice Age. As the ice sheet retreated, the rodent population on the freshly thawed steppe would have exploded, creating an urgent need for a Malthusian pruning mechanism. The development of agriculture, another demographic landmark in rodent history, would have further heightened the need for such an agent.

Y. pestisis only fifteen hundred to twenty thousand years old, young enough to fit Dr. Brubaker’s scenario, and its ragged genetic structure certainly suggests an agent slapped together in a hurry to meet an evolutionary emergency.Y. pestis’s genome has a great many nonfunctioning genes and three ungainly plasmids. However, in pathogens as in people, appearances can be deceiving.Y. pestishas all the properties an infectious agent needs to be a world beater, including biological oomph. One reason many infectious agents fail to rise to the level of lethality is that their bacilli cluster together at an infection site (like a flea bite), instead of spreading to vital body organs. Consequently, nothing more serious than some local swelling and redness develops.Y. pestishas solved the cluster problem by evolving special enzymes that deliver plague bacilli to the liver and spleen, from whence the bacilli can be quickly recycled to the rest of the body. Equally important, the bacillus has also learned how to elude almost everything sent to kill it, including flea antigens and human antigens. In the case of flea antigens, the elusiveness givesY. pestistime to multiply in the flea gut, which is a key step in the transmission of plague. In the case of the human antigens, the elusiveness buys the pathogen time to jump from the lymph nodes to the liver and spleen. Like HIV,Y. pestisis extremely adept at confusing the human immune system. Often by the time the body can mount a defense, the pathogen has become uncontainable.

Y. pestiscan also kill nearly anything put in front of it, including humans, rats, tarabagans, gerbils, squirrels, prairie dogs, camels, chickens, pigs, dogs, cats, and, according to one chronicler, lions. Like other major pathogens,Y. pestishas become a successful killer by learning how to be an adaptable killer. It can be transmitted by thirty-one different flea species, includingX. cheopis,the most efficient vector in human plague, andPulex irritans,the most controversial. Some researchers believe the bite of the ubiquitousP. irritans,the human—and pig—flea, contains too few bacilli to transmit plague effectively; but other investigators* suspect that the human flea plays an important, if unappreciated, role in the spread of the disease. The pro–P. irritansschool is supported by the work of General Shiro Ishii, commander of the Japanese army’s biological warfare unit during World War II.*

Assessing the Japanese deployment of a plague weapon against the Chinese city of Changteh early in the war, an admiring U.S. Army report notes that “one of Ishii’s greatest achievements . . . was his use of the human flea,P. irritans. . . . This flea is resistant to air drag, naturally targets humans, and could also infect the local rat population to prolong the epidemic. . . . Within two weeks [of the attack] individuals in Changteh started dying of plague.”

Y. pestisdoes have limitations. It cannot survive very long on surfaces like chairs, tables, and floors, and it operates optimally only within a fairly narrow climatic range—air temperatures between 50 and 80 degrees Fahrenheit and humidity above 60 percent and, ideally, 80 percent. A number of animals are also resistant to the plague bacillus, including the Siberian polecat, black bear, skunk, and coyote. Man may also enjoy a degree of immunity toY. pestis,though that is another question fraught with controversy. Despite a recent finding suggesting that CCR5-∆32, the allele that protects against HIV, may also protect against plague, many scientists remain skeptical of humanity’s ability to resistY. pestis,except for a temporary resistance acquired after exposure to the disease.

Among the species that do develop at least a partial immunity toY. pestisis its host population, rodents. Indeed, the plague bacillus’s exquisite attunement to the rodent community is one of the great marvels of nature. Most of the timeY. pestisand the rodent kingdom live in a state of unhappy but workable coexistence. The scientific term for the modus vivendi is enzootic. Animals continue to get sick and die, but usually there are enough partially resistant rodents in any given community to keep the smoldering embers of infection in check. There are a number of theories about why, from time to time, this biological firewall suddenly collapses and the colony is consumed by the flames of an epizootic—a full-scale outbreak of plague. These include genetic change in the plague bacillus, which makes it more virulent, and demographic changes in the wild rodent community, which make its members more vulnerable to plague. A third theory, not incompatible with the first two, is that epizootics are activated by surge years—sudden, dramatic spurts in the rodent population. No one is sure what causes surges, but a number of scientists believe that they may be related to sun spots, which follow roughly the same cyclical pattern as surge years in many (though not all) rodent species, approximately ten to twelve years.

The connection is not as odd as it sounds. Sun spot cycles—which influence rainfall, tropical cyclones, and tree growth—may affect the wild rodent food supply. Climate changes may make vegetation more abundant, encouraging a burst of overbreeding, perhaps by affecting rodent fertility. Certain species of hare are known to experience cyclical bursts of fecundity. Clearer is what happens during a surge year; rodent populations breed themselves into a classic Malthusian dilemma: too many animals, too little food. And, as Malthus noted, when that happens nature usually prunes the population back to a sustainable level by way of a major demographic catastrophe, such as a famine or infectious disease. In the case of rodents, one component of the pruning mechanism may be an alteration in the community’s genetic composition. As rodent numbers spike during the surge, the pool of older, partially immune animals—the community firewall—is diluted by a rapidly expanding group of younger animals who have not yet acquired resistance toY. pestis.This pool of unprotected young may constitute the biological equivalent of an oil slick; throw a match on it and it bursts into flame.

Aside from providing an insight into nature’s secret harmonies, the dynamics of rodent populations would not matter much to humans but for the fact that during surge years towns, villages, and campsites are more likely to be invaded by hungry rodents. In one thirty-four-year period on the eastern steppe, four of five plague outbreaks occurred in tarabagan surge years, and the victims were local hunters, men schooled in the dangers of trapping sick animals. If experienced steppe veterans proved vulnerable toY. pestis,it does not take a large leap to imagine what would happen to a group of unwary outsiders unlucky enough to brush up against a tarabagan community in Mongolia, Manchuria, or Siberia in the midst of a surge year, particularly if the tarabagans’ food supply was under threat not only from the demographic pressures of the surge but also from long-term ecological changes.

Indeed, it is not even necessary to imagine what might happen; a historical precedent is available. Between 1907 and 1910, the world price of tarabagan skins quadrupled from 0.3 rubles to 1.2 rubles, producing a corresponding increase in the number of tarabagan hunters. Many of the newcomers were unskilled Chinese, looking to turn a fast ruble and ignorant of steppe lore about hunting staggering tarabagan. In April 1910 pneumonic plague broke out among a colony of hunters in Manchuria; within a year sixty thousand people were dead.

In the case of the Black Death, the first group of outsiders to be infected may have been Mongol herdsmen looking for new pastureland. During the fourteenth century, the wind patterns of Eurasia changed, altering the climate of the continent; Europe became wetter, while Asia became drier. The arrival of desertlike weather in the East may have forced Tartar herdsmen out of their traditional pasturelands and into the “tarabagan gardens” of the northern steppe, a region whose dangers they were as ignorant of as were the Chinese hunters in early-twentieth-century Manchuria. From the herdsmen, the plague would have spread to other outsiders: Arab, Persian, Italian, or Central Asian merchants; Tartar horsemen and soldiers; Chinese or Ukrainian laborers—or some combination of all or most of the above. Also easy to imagine is how political and economic changes like the rise of the Mongol Empire and the development of a nascent global economy would have allowedY. pestisto overcome the vast distances, thin populations, and other firewalls that had kept it trapped in the remoteness of inner Asia for centuries. After unifying the fractious steppe under apax Mongolica,the Tartars threw several overlapping communication networks across the vast, open prairies of Asia and Russia, including the Yam, a pony express service, new trade routes, and a network of caravansaries.

William McNeill, author ofPlagues and Peoples,thinks the caravan rest stops may have played a key role in the early spread of plague. “Assuredly the far-flung network of caravanserais extending throughout Central Asia . . . made a ready made pathway for the propagation of [plague] across thinly inhabited regions. Each resting spot for caravans must have supported a complement of fleas and rats attracted there by the relative massive amount of foodstuffs necessary to keep scores even hundreds of travelling men and beasts going.”

If the Black Death originated in or near the Gobi desert,Y. pestiswould have visited a half dozen such rest stops before climbing a mile in the sky to Lake Issyk Kul, the hot lake where it first burst into history. Warmed by thermal springs that can produce water temperatures of 85 to 95 degrees Fahrenheit, Issyk Kul sits five thousand feet above sea level in a bowl of snow-capped mountain and thick forest. Today the lake region is full of ghosts—Soviet, czarist, even a few Tartar, including the ripply outlines of a submerged village a few hundred feet from the shoreline. But in the mid-fourteenth century, Issyk Kul was a bustling trading center astride the northern steppe route. From the region, eastbound travelers could pick up the fast road into China; westbound travelers, the road home to Caffa, Tabriz, or Baghdad. Medieval Issyk Kul also had a substantial local population. Many of its inhabitants were Nestorians, a Christian sect of Syrian origin that spread across Asia in the early Middle Ages. On arriving in China, evangelical pioneers like John of Monte Corvino were astonished to see church spires rising above cities like Hangchow. “We have found many Christians scattered all over the east and many fine churches, lofty, ancient and of good architecture,” declared one Western visitor.

The Nestorians were both an accomplished and a flowery people. The inscriptions on the headstones found in two local Issyk Kul cemeteries speak in the florid language of the funeral oration. One informs the passerby: “This is the grave of Shliha, the celebrated commentator and teacher, who illuminated all the monasteries with light. . . . His voice rang as high as a trumpet.” Another: “This is the grave of Pesoha, the renowned evangelist and preacher who enlightened all. . . . Extolled for wisdom and may our Lord unite his spirit with the saints.”

In comparison, the inscription on a third Nestorian headstone, that of a husband and wife, Kutluk and Magnu-Kelka, has an almost ominous starkness. No accomplishments are mentioned, no holiness praised. The headstone tells us only enough to suggest the following scenario: one morning in 1339, perhaps a fragrant early-summer morning when the air temperature almost matched the water temperature on the lake, Kutluk awoke with the early symptoms of plague. On that first day he felt lightheaded and nauseous, symptoms so unobtrusive Magnu-Kelka did not even realize her husband was ill until dinner, when Kutluk suddenly vomited into his meal. On the second day of his illness, Kutluk awoke with a terrible pain in his groin; overnight, a hard, apple-sized lump had formed between his navel and his penis. That afternoon, when Magnu-Kelka probed the tumor with a finger, the pain was so terrible, Kutluk rolled over on his side and vomited again.

Toward evening, Kutluk developed a new symptom; he began to cough up thick knots of bloody mucus. The coughing continued for several hours. As night gathered around the lake, a sweaty, feverish Kutluk fell into a delirium; he imagined he saw people hanging by their tongues from trees of fire, burning in furnaces, smothering in foul-smelling smoke, being swallowed by monstrous fish, gnawed by demons, and bitten by serpents. The next morning, while Kutluk was reliving the terrible dream, the cough returned—this time even more fiercely. By early afternoon, Kutluk’s lips and chin had become caked with blood, and the inside of his chest felt as if it had been seared by a hot iron. That night, while Magnu-Kelka was sponging Kutluk, the tumor on his groin gurgled. For a moment Magnu-Kelka wondered if the swelling were alive; quickly, she made the sign of the cross. On the fourth day of his illness, Kutluk stained his straw bed with a bloody anal leakage, but Magnu-Kelka failed to notice. After vomiting twice in the morning, she slept until dark. When she awoke again, it was to the sound of crickets chirping in the evening darkness; she listened for a moment, then vomited on herself. On the fifth day of his illness, Kutluk was near death. All day Magnu-Kelka lay on a straw mat on the other side of the cottage, listening to her husband’s hacking cough and breathing in the fetid air. Toward evening Kutluk made a strange rattling sound in his throat and the cottage fell silent. As Magnu-Kelka gazed at her husband’s still body, she felt an odd sensation—like the fluttering of butterfly wings against the inside of her chest. A moment later, she began to cough.

Kutluk and Magnu-Kelka were almost certainly not the first victims of the Black Death, but their remote little lakeside cottage is where the most terrible natural disaster in history begins to enter the human record.

Two other notable names in the history of plague are Justinian, the sixth-century Byzantine emperor, and Alexandre Yersin, a dreamy young Swiss scientist who became the Yersin inYersinia pestisduring the Third Pandemic of a century ago. The human equivalent of an epizootic, a pandemic is a catastrophic outbreak of infectious disease; including the Black Death, three times in recorded human history plague has risen to the level of pandemic. The first time, the Plague of Justinian, is where the story of man andY. pestisbegins, and the last time, the Third Pandemic, is where the mysteries of the plague bacillus were finally unraveled. The reemergence of large-scale pestilence in late-nineteenth-century China horrified the self-confident Victorians, occasioning an early example of what today is called Big Science. In the 1890s, asY. pestisswept through China and India, researchers from dozens of countries focused their energies on a single, urgent question: “What causes plague?”

In the end, the worldwide race narrowed down to one city, Hong Kong, and two young men, each a surrogate for the two great microbiologists of the Victorian age, the Frenchman Louis Pasteur and the German Robert Koch. Koch’s surrogate, a former student named Shibasaburo Kitasato, was a heavyset, ambitious young man who wore a starched wing-tip collar even in the sultry Hong Kong heat and enjoyed the seemingly unbeatable advantages of modern equipment, a large staff, and devious mind. Pasteur’s surrogate was the moony Yersin, a Somerset Maugham-ish figure, who gave up a life of privilege in the West to search for Higher Truth in the East. In a film about the race to identifyY. pestis,Leslie Howard would have played Yersin.

Despite having fewer resources and lacking the inspired duplicity of Kitasato (“The Japanese . . . have bribed the staff of the hospital so that they will not provide me with [any bodies for] autopsy!” Yersin complained to his mother), the young Swiss investigator became, in 1894, the first person to accurately describe the plague pathogen. “The pulp of the buboes always contains short, stubby bacilli,” he noted in one of the most important papers ever written about human disease. A few years later a Frenchman named Paul-Louis Simond identified the rat and rat flea,X. cheopis,as plague vectors. In 1901 Kitasato’s mentor, Robert Koch, summarized the new research this way. Plague, said Koch, is “a disease of rats in which men participate.” A few decades later the first effective antiplague medications began to become available.

If the Third Pandemic is where the story of man and plague ends—at least for now—then the sixth-century Plague of Justinian is where it begins. There are several references to what sounds like plague in the Bible, butY. pestisdid not officially enter human history until a.d. 542, when it strode off a ship in the Egyptian port of Pelusium. From a modern perspective, the most striking thing about the Plague of Justinian is how closely it resembles the Black Death. There is, first of all, the crucial role of commerce in disseminating disease. Until a trade route from Egypt made it more accessible, Ethiopia, the probable home of the First Pandemic, was as remote from the major population centers of late Antiquity as the other plague foci of the premodern world: the Eurasian steppe (including Siberia and the Gobi desert), Yunnan in China, and perhaps Kurdistan in Iran. Like the Black Death, the Plague of Justinian also occurred during a period of extreme ecological change. A recent study of two thousand years of tree ring data reveals that four years in the last two millennia were periods of extraordinarily severe weather, and two of those four years were situated in or around a plague pandemic. One was 1325, roughly the timeY. pestismay have been at work on the rodent population of the Gobi or some other region of inner Asia; the other was 540, two years beforeY. pestisarrived in Pelusium, and roughly around the time that Chinese scribes were describing yellow dust falling like snow and Europeans were complaining about the bitter cold that ushered in the Dark Ages. “The winters [are] grievous and more severe than usual,” wrote the sixth-century monk Gregory of Tours. “The streams are held in chains of frost and furnish . . . a path for people like dry ground. Birds too [are] affected by the cold and hunger and [are] caught in the hand without any snare when the snow [is] deep.”

In the Plague of Justinian, one also hears for the first time a sound that becomes overpowering during the medieval pestilence: the sound of human beings drowning in death. “At the outset of this great misfortune,” wrote a lawyer named Evagrius, “I lost many of my children, my wife and other relatives and numerous estate dwellers and servants. . . . As I write this in the 58th year of my life . . . I [have recently] lost another daughter and the son she has produced quite apart from other losses.”

No one knows how many people died in the Plague of Justinian, but in Constantinople, where the daily mortality rate is said to have reached ten thousand at the peak of the epidemic, people put on name badges so that they could be identified if they fell on the streets. The mortality was also very severe in the Middle East. “In every field from Syria to Thrace the harvest lacked a harvester,” wrote John of Ephesus, who went to bed each night expecting to die and awoke each morning surprised to find himself still alive. Untold thousands also perished in Italy and in France, where Gregory of Tours reported that “soon no coffins or bearers were left.”

The Plague of Justinian marked an important turning point in Europe’s relationship with infectious disease. The centuries preceding the First Pandemic were a period of chronic, devastating epidemics. In the second and third centuries, smallpox and measles outbreaks may have killed a quarter to a third of the population in parts of the Roman Empire. The centuries after Justinian were, if not disease-free, then close to it. During the early Middle Ages, all forms of infectious illness became uncommon and plague (as far as is known), nonexistent. For this disease-free interim, the collapse of civilization deserves some credit. A disease is more than just a pathogen plus a transportation system. To ignite an epidemic, a friendly environment is also necessary, and after Rome fell, the environment in Europe, particularly northwest Europe, became increasingly unfriendly to epidemic disease. In the early Middle Ages, the population plunged precipitously, shrinking the pool of potential host-victims. In the second and third centuries, Roman Europe had 50 to 70 million people; by 700, Europe had 25 to 26 million. The disappearance of urban life removed two other necessities: concentrations of people, and filthy, rodent-infested streets. At its height, the city of Rome had a population variously estimated at half a million to ten million; by 800, no city in Europe contained more than twenty thousand residents. “In the middle of the debris of great cities,” wrote one Dark Ages scribe, “only scattered groups of wretched peoples survive.”

The resurgent forest provided a further barrier against infectious illness. By a.d. 800, dense woodland had reclaimed 80 percent of a depopulated Europe’s surface, severely restricting trade and travel and providing a firewall, which helped to keep local epidemics local. The international situation added a final layer of insulation. By the ninth century, the principal east-west trade routes were all in unfriendly Muslim hands.

Around the year 1000, this process began to reverse itself and Europe started to re-create the environmental conditions associated with demographic collapse in premodern societies. And indeed, four hundred years later the West would suffer a second great demographic catastrophe, but that gets us ahead of our story, which begins where stories of pandemics often do: in a burst of human progress.

Sometime between 750 and 800, Europe entered the Little Optimum,* a period of global warming. Across the continent, temperatures increased by an average of more than 1 degree Celsius, but, rather than producing catastrophe, as many current theorists of global warming predict, the warm weather produced abundance.* England and Poland became wine-growing countries, and even the inhabitants of Greenland began experimenting with vineyards. More important, the warm weather turned marginal farmland into decent farmland, and decent farmland into good farmland. In the final centuries of Roman rule, crop yields had fallen to two and three to one—a yield represents the amount of seed harvested to the amount planted: a return so meager, the Roman agricultural writer Columella feared that the land had grown old. In the eleventh and twelfth centuries, as winters became milder and summers warmer and drier, European farms began to produce yields of five and six to one, unprecedented by medieval standards.

A burst of technological innovation added to agricultural productivity. Someone figured out that one easy (and cheap) way to get a horse to pull more was to redistribute weight away from its windpipe, so when it moved forward it wouldn’t choke. Thus was born the horse collar, which increased horsepower by a factor of four. Another simple innovation, the horseshoe, increased it even more, by improving the horse’s endurance. The newcarrucaplow, with its large, sharp rectangular blade, also represented an important improvement, particularly in northern Europe, where the soil was heavier and harder to turn. However, the true technological marvels of the age were the watermill and the windmill; for the first time in human history, a society had harnessed a natural source of power. “Behold,” wrote an admiring monk, in a soliloquy to his abbey’s watermill, “the river . . . throws itself first impetuously into the mill . . . to grind the wheat . . . separating the flour from the bran. [Then] . . . [it] fills the cauldron . . . to prepare drinks for the monks. . . . Yet, the river does not consider itself discharged. The fullers [wool workers] near the mill call [it] to them. . . . Merciful God! What consolations you grant to your poor servants.” Another important innovation was a new crop rotation system, which kept more of the land under cultivation during the year.

As agricultural productivity improved, living standards rose, producing a baby boom of historic proportions. The demographic surge of the Central Middle Ages was as dramatic as the decline of five hundred years earlier. Between 1000 and 1250 the population doubled, tripled, and may even have quadrupled. Around 1300 Europe held at least seventy-five million—and some scholars think as many as a hundred million—people, up from twenty-six million during the Dark Ages.* In France the population jumped from five million to about sixteen to twenty-four million; in England, from a million and a half to five to six to seven million; in Germany, from three million to twelve million; and in Italy, from five million to ten million. In 1300 parts of Europe were more populous than they would be again until the eighteenth and nineteenth centuries. Britain, for example, would not see six million people again until the American Revolution, and France would not reach seventeen million again until Napoleon’s time, while Tuscany would not have two million inhabitants again until 1850.

As the population soared, urban life reawakened. Pre–Black Death Paris had about 210,000 residents; Bruges, site of the rapidly growing cloth industry, 50,000; London, 60,000 to l00,000; and Ghent, Liege, and Ypres, 40,000 each. In Florence, banker Giovanni Villani boasted that “five to six thousand babies are born in the city each year.” But Florence, with a population of 120,000, took a backseat to Milan, with its population of 180,000. Siena, Padua, Pisa, and Naples were the little brothers of the Italian peninsula, with populations of 30,000-plus, but even they would have been major cities in the year 1000.

The medieval countryside also filled up. In Germany’s Moselle Valley, the 340 villages of the year 800 quadrupled to 1,380 villages by 1300. Many parts of rural France experienced equally spectacular growth; Beaumont-le-Roger county in Normandy would not have thirty thousand residents again until the twentieth century; and San Gimignano, in Tuscany, is still smaller than it was in 1300.

In the village of Broughton in England, the population reached a medieval high of 292 souls around 1290.

As the population went up, the forests came down. During the Great Clearances of the twelfth and thirteenth centuries, Europeans burst out of the enormous woodlands that had held them prisoner since the Dark Ages and began to reassert human dominance over the environment. From Scotland to Poland, the great dark woods echoed with the song of human progress: sawing and banging, and the boom and thud and thump of falling timber. Swamps were drained, pastures cleared, fields laid out, crops planted, homes built, and villages erected. Sunlight fell on land that had not felt its warmth since before Justinian’s time. Under the press of an expanding population, the continent also thrust outward. In the south, land-hungry Christian kings and colonists—their hearts full of God and avarice—pushed the once invincible Muslims down the Spanish peninsula until, by 1212, only Grenada on the southern tip of Iberia failed to fly the flag of the “Reconquista.” In the East, German and Flemish colonists pushed across the Elbe to settle the still-dense forests of eastern Germany and Prussia; in the Danube Valley, streams of carts and horses were flowing into what would become Austria and Hungary.

As the population grew, trade revived. In the year 1000 an Italian merchant had virtually no chance of doing business in England. By 1280 a trader—or a pathogen—could travel though a reinvigorated, reconnected Europe with relative ease. The Atlantic and Mediterranean regions were linked by a land route that wound through the meadows of the high Alpine passes and a sea route that looped around the Pillars of Hercules—Gibraltar—and ended in the busy port of London, where dinosaur-necked wooden cranes were used to unload arriving ships. There were also dozens of new regional trade networks: some originated in Flanders, home of a wealthy new bourgeoisie mad for jewels and spices; some in Germany, seat of the Hanseatic League, an association of Baltic merchants. Another important commercial network sprang up around Champagne, site of the Champagne (Trade) Fairs where, once a year, local servant girls, laundresses, and tradeswomen would become prostitutes-for-a-day to entertain merchants from as far away as Iceland, and where crafty Sienese and Florentine bankers offered loans with so many strings attached that a borrower could be excommunicated from the Church and face eternal damnation should he default.

From the bustling ports of Venice and Genoa, another set of trade routes led southeastward across the Mediterranean to the great trading cities of the Middle East, where the air smelled of mango and palm and the call to prayers echoed through alabaster streets five times a day. In Alexandria (Egypt), in Aleppo (Syria), in Acre or Tyre (the Kingdom of Jerusalem), a shopper could buy sugar from Syria, wax from Morocco and Tunis, and camphor, alum, ivory tusks, muslin, ambergris, musk, carpets, and ebony from Quinlon, Baghdad, and Ceylon—but, alas, were he a Christian shopper, only at unconscionably high prices. In Alexandria, local tolls added 300 percent to the price of Indian goods, and that 300 percent was in addition to the enormous markup that the Arab middlemen took off the top.

Early in the thirteenth century the Venetians, who described themselves as “rulers of half and a quarter of the Roman Empire,” devised an ingenious bit of mischief to circumvent the greedy Arabs and deal directly with the East. Venetian authorities offered a group of French Crusaders free passage to the Holy Land, then rerouted the Crusaders east to capture Constantinople. While the plan succeeded brilliantly—the Venetians even managed to steal four great gilded horses for St. Mark’s Cathedral—Constantinople, where the rival Genoese soon had a base, was still a long way from the timber, fur, and slaves of the Crimea and southern Russia, farther away from the great market towns of Central Asia like Samarkand and Merv, and light-years away from the emerald city of Hangchow.

For the “two torches of Italy,” as Petrarch called Venice and Genoa, the Bosporus nights were full of frustration and longing—but relief was nigh.

According to legend, on a cold morning in 1237, three anonymous riders emerged out of a lightly falling snow in front of Ryazan, a town near the eastern border of medieval Russia. The small party halted for a moment; then one rider broke free and dashed across the snowy ground toward Ryazan, shouting. Attracted by the noise, a crowd gathered at the town gate. “A witch,” said one townsman, pointing at the rider, who had turned out to be a woman of astonishing ugliness. “No,” said a second townsman, “a sorceress.” As the two argued, the rider continued to dash back and forth in front of Ryazan, shouting, “One-tenth of everything! Of horses, of men, of everything! One tenth!”

In a second version of the Sorceress of Ryazan story, the female rider, apparently selected for her knowledge of the local dialect, demanded “one tenth of everything” from a group of Russian princes gathered in Ryazan. But in both versions, the end is the same. The Tartar demand for tribute is spurned, the mysterious sorceress vanishes, and her visit is forgotten.

Then, on a winter morning a few months later, a thunderous rumble awakens the town. Doors fly open, heads appear, half-dressed men rush into the street. Someone shouts; fingers point. To the east, a black band of horsemen is hurtling across the horizon toward Ryazan under a dawn sky. Hurriedly, children are slipped under floorboards or hidden under blankets and quilts; doors are bolted; swords unsheathed, prayers whispered. As the short-legged Mongol ponies clear the earthworks in front of Ryazan, the morning streets fill with slashing, cutting horsemen. People scream, body parts fly, pools of blood form in the fresh snow. Plumes of black smoke rise into a vermilion sky. All morning and into the early afternoon, under a dim winter sun, Ryazan is methodically, systematically exterminated. Children are killed along with parents, girls along with boys, old along with young, princes along with peasants. Later a Russian chronicler will write that the citizenry was slaughtered “without distinction to age or rank.”

Ryazan was not the Mongols’ first appearance on the western steppe. Twenty years earlier, the Tartars had made another brief foray into medieval Russia, but that raid had been more in the nature of an evil rumor. Afterward the chronicler of Novgorod wrote, “For our sins, unknown tribes came among us. . . . God alone knows who they are or where they came from.” By contrast, Ryazan was part of a grand design of world conquest. Genghis Khan means “Emperor of Mankind,” and though the founder of the Mongol Empire was ten years dead when Ryazan fell, his universalist ambitions lived on in his sons and grandsons. After subduing most of northern China in the 1210s and Central Asia in the 1220s, the Mongol leadership held akuriltai(grand assembly) in 1235, where it was decided to move against the West.

Europe knew nothing about thekuriltai,but during the 1230s enough rumors had drifted westward across the steppe to create a profound sense of unease. There were stories of terrible massacres in Central Asia and, after Ryazan and other Russian towns fell, almost daily rumors of a Tartar invasion. In 1238 the fisheries of Yarmouth shut down because their German customers had become too frightened to travel. In the late 1230s the immediacy of the danger was underscored when one of Christendom’s most implacable foes, the “Old Man of the Mountain,” leader of the fanatical Muslim “Assassins of Iran,” reportedly sent an envoy to Europe to propose a joint alliance against the Tartars. Whether true or only a rumor, the story was as shocking to contemporaries as the Hitler-Stalin pact was in its time.

On April 9, 1241, with a conquered Russia in ruins, the cream of European arms gathered on a Polish field to meet the Mongol onslaught. After the battle, the Tartars sent home nine sacks of ears. Two days later a large Hungarian army was crushed at Mohi; shortly thereafter, a small Tartar force appeared in the vicinity of Vienna. As eastern Europe filled with refugees, panic gripped western Europe. In Germany rumors that the Tartars were Gog and Magog, the two lost tribes of Israel, ignited pogroms against the Jews. In France a knight warned Louis IX that the Mongols would soon be on the Somme. In England the monk Matthew Paris predicted a bloodbath of unimaginable proportions. The Mongols, he said, are “monsters rather than men, . . . inhuman and beastly, thirsting for and drinking blood and devouring the flesh of dogs and men, and striking everyone with terror and incomparable horror.”

In Rome the pope received a letter from Grand Khan Ogedi. It read: “You personally, as the head of all kings, you shall come, one and all, to pay homage to me and serve me. Then we shall take note of your submission. If . . . you do not accept God’s order, we shall know that you are our enemies.”

However, Europe’s string of good fortune had not quite run its course. Just as the apocalypse seemed about to burst upon Christendom, dissension erupted in the Mongol royal family and offensive operations were halted in the West. This provided a breathing space for clerical visitors like William to improve relations between East and West. Thus, in the 1250s, when the Mongols next went on the offensive, it was not against Christendom, but against an older enemy. In the 1220s the Mongol hordes had crushed Islamic power in Central Asia; now they would crush it again, this time in the Muslim heartland, the Near East and Middle East.

On hearing of Baghdad’s fall in 1259, a Christian chronicler exulted: “Now, after five hundred years, the measure of the city’s inequity [is] fulfilled and she [is] punished for all the blood she [has] shed.”

A decade later, the Genoese were in Caffa and the Venetians in Tana at the mouth of the Don, and a few years after that young Marco Polo was crossing the Gobi Desert, observing the local wildlife. The ubiquitousness of one species in particular struck him. “There are great numbers of Pharaoh’s rats in burrows on [these] plains,” he noted.

“Pharaoh’s rat” was a medieval term for the tarabagan.