The inhospitable, remote high steppes and grassland of the austere and windswept northern Asian plateau were occupied by warring tribal clans and duplicitous factions. Alliances were capricious, changing course as swiftly as the whims of the blustery winds. Temujin was born into this unforgiving region in 1162 and reared in a clan-based society that revolved around tribal raids, plundering, revenge, corruption, and, of course, horses.

After his father’s capture by rival clans, Temujin and his family were reduced to dire poverty, scavenging for wild fruits and grasses, feeding on the carcasses of dead animals, and hunting small marmots and rodents. Then, with the death of his father, his clan had lost prestige and clout in the larger alliances and political arenas of Mongol tribal power. In this moment of desolation and despair, Temujin could not know that from these scraping, humble origins he would secure fame and fortune and a new name that would strike fear into the hearts of his enemies during his campaigns for world domination.

Vying to restore his family’s honor, Temujin, now fifteen years old, was captured during a raid by his father’s former allies. He successfully escaped from enslavement, and vowed revenge on his opponents, now a long list consisting of both traditional enemies and previous partners. Although Temujin was loath to share authority, he recognized that ultimate power and prestige, as he had been instructed by his mother as a boy, rested on numerous strong and stable alliances.

In his quest to unite the warring factions, Temujin broke from Mongol tradition. Rather than killing or enslaving those he conquered, he promised them protection and the spoils of war from future conquests. Appointments to senior military and political positions were based on merit, loyalty, and acumen rather than clan affiliations or nepotism.

The Rise of Genghis Khan

These social ingenuities strengthened the cohesion of his confederacy, inspired loyalty from those he conquered, and augmented his military might as he continued to incorporate Mongol clans into his increasingly powerful alliance. As a result, by 1206, Temujin had united the warring tribes of the Asian steppes under his rule and created a formidable, cohesive military and political force that would eventually annex one of the largest empires in history.

He ultimately brought Alexander’s mosquito-deterred dream—the bridging of the “ends of the earth” from Asia to Europe—into reality. The mosquito, however, haunted his own visions of grandeur and glory just as she had haunted Alexander 1,500 years earlier.

By this time, his Mongol subjects had given Temujin a new name— Genghis Khan, or the “Universal Ruler”. After completing his coalition of the competing and combative Mongol tribes, Genghis (or Chingiz) and his skillful mounted archers initiated a flurry of quick-striking outward military campaigns to secure living space . . . and then some.

Genghis Khan proclaimed Khagan of all Mongols. Illustration from a 15 th century Jami' al-tawarikh manuscript. (Oltau / Public Domain )

Mongol expansion under Genghis Khan was in part the result of the mini ice age. This mercury-dipping climate change drastically reduced grasslands that sustained their horses and their mounted nomadic way of life. For the Mongols, it became expand or expire. The astonishing speed of the Mongol advance was due to Genghis Khan’s military abilities and that of his generals, an impressively cohesive military command and control structure, wide-swath flanking techniques, specialized compound bows, and, most of all, their unparalleled skill and dexterity as horsemen.

By 1220, the Mongol Empire stretched from the Pacific coasts of Korea and China, south to the Yangtze River and the Himalayan Mountains, reaching the Euphrates River in the west. The Mongols were true masters of what the Nazis later called Blitzkrieg or “lightning war”. They encircled their hapless enemies with breathtaking, unrivaled speed and ferocity.

In 1220, Genghis divided his army into two prongs, and accomplished what Alexander could not—the binding together of the two halves of the known world. For the first time, the east officially met the west, albeit in cruel and hostile circumstances. Genghis led the main army back east through Afghanistan and northern India toward Mongolia.

A second army of roughly 30,000 horsemen punched north through the Caucasus and into Russia, sacking the Italian trading port of Kaffa (Feodosia) on the Crimean Peninsula of the Ukraine. Throughout European Russia and the Baltic states, the Mongols routed the Rus, the Kievans, and the Bulgars. Local populations were ravaged, murdered, or sold into slavery and little quarter was given to opposing soldiers.

When the dust settled and the Mongol hoofbeats drummed in the distance, upwards of 80% of the local populations had been killed or enslaved. The Mongols probed Poland and Hungary to gather intelligence before quickly retreating east in the summer of 1223 to join Genghis’s Mongolia-bound column.

Why the Mongols decided to forsake Europe is subject to debate. It is widely held that the final strokes of this campaign were intended to be nothing more than reconnaissance missions for a future full-scale invasion of Europe. Historians have also suggested that the decision to postpone an invasion was based on the weakening of the Mongol army from malaria contracted in the Caucasus and along the river systems of the Black Sea, magnified by nearly twenty years of perpetual warfare.

It is known that Genghis himself was suffering from habitual bouts of malaria at this time. The most generally accepted theory is that his death at sixty-five years old was the result of stubborn, festering wounds caused by the severe weakening of his immune system at the hands of chronic malarial infection.

The great warrior died in August 1227 and, in keeping with cultural norms, was buried without fanfare or marker. Legend has it that the small burial party killed anyone they met en-route to conceal his final resting place, diverted a river over the grave, or alternatively, branded it into historical oblivion with stampeding horses.

Like Alexander, the body of the Great Khan has been lost to legend and lore. All attempts and expeditions to locate his grave have ended in disappointment. The mosquito’s thirst for Mongol blood, however, was not yet slaked, and she would continue to saddle his imposing empire.

Mongol Hordes Smash into Europe

Under Genghis’s son and successor , Ogedei, the Mongols launched an unrestrained counterclockwise assault on Europe between 1236 and 1242. The Mongol hordes quickly smashed their way through eastern Russia, the Baltic states, the Ukraine, Romania, Czech and Slovak lands, Poland, and Hungary, reaching Budapest and the Danube River on Christmas Day 1241. From Budapest they continued their western drive across Austria, before heading south, and eventually back east, ransacking their way across the Balkans and Bulgaria.

Coronation of Ogedei Khan in 1229 new ruler of the Mongol Empire. (World Imaging / Public Domain )

Continuing east, in 1242, the Mongols abandoned Europe, never to return. The invincible Mongols, as it turns out, could not defeat the mosquito and break her dogged defense of Europe.

Of this seemingly impulsive and surprising retreat Winston Churchill wrote, “At one moment it had seemed as if all Europe would succumb to a terrible menace looming up from the east. Heathen Mongol hordes from the heart of Asia, formidable horsemen armed with bows, had rapidly swept over Russia, Poland, Hungary, and in 1241 inflicted simultaneous crushing defeats upon the Germans near Breslau and upon European cavalry near Buda. Germany and Austria at least lay at their mercy. Providentially . . . the Mongol leaders hastened back the thousands of miles to Karakorum, their capital . . . and Western Europe escaped”.

Mosquitoes Save Europe

During the summer and fall of 1241, the majority of the Mongol forces were resting on the Hungarian plains. Although the previous years had been unseasonably warm and dry, the spring and summer of 1241 were unusually damp, with higher amounts of precipitation than usual turning the formerly dry Magyar grasslands of eastern Europe into a marshy morass and a minefield of malarial mosquitoes.

For the Mongol military machine, the negative repercussions of this climate change created the perfect storm to shelter Europe. For starters, the quagmire and high water table robbed the Mongols of the essential grazing grounds and pasturelands for their innumerable horses, which were the crux of their military prowess. The unusually high humidity also caused Mongol bows to falter.

The negative repercussions of the climate of Europe caused Mongol bows to falter. (Yaan / Public Domain )

The stubborn glue refused to coagulate and dry in the moist air, and the diminished tautness of their heat-expanding bow strings negated the Mongol advantage of increased velocity, accuracy, and distance. Compounding these military drawbacks was a bursting population of parched mosquitoes. The malaria parasite began its artful invasion of their virgin veins.

The Mongol hordes, writes acclaimed historian John Keegan, “ferocious though they were, ultimately failed to translate their light cavalry power from the semi-temperate and desert regions where it flourished in to the high-rainfall zone of Western Europe, they had to admit defeat”.

While the Mongols, and accompanying traders like Marco Polo , finally united the east and west, the mosquito helped prevent the west from being completely overrun. She harnessed her malarial might and held the reins of Mongol conquest, steering them away from Europe.

While the mosquito sucked dry their dreams of European subjugation, the Mongols, under Kublai Khan , the grandson of Genghis, launched their first campaign into the Holy Land in 1260, adding another contender to the ongoing, yet moribund, Crusades. Their entrance into this flagging competition occurred during the intermission between the Seventh (1248–1254) and Eighth (1270) Crusades.

Malaria Ravaged Armies

Indicative of the confusion engulfing the later Crusades, over the next fifty years, which witnessed four major Mongol invasions, alliances among the Muslims, Christians, and Mongol factions shifted and allegiances were regularly realigned and calibrated. Just like the mosquito, yesterday’s friend colluded today to become tomorrow’s foe. In fact, on numerous occasions, offshoots from each power lined up on opposite sides, as inner turmoil rankled and unraveled the cohesion of the three dominant groups.

Although the Mongols did have some limited success, including brief stopovers in Aleppo and Damascus, they were repeatedly forced to retreat in the face of malaria, additional disease, and powerful defensive coalitions. General Anopheles, the guardian of Christian Rome, also garrisoned the Holy Land for Islam.

As she had done during earlier Christian campaigns, including Richard the Lionheart’s mosquito-racked Third Crusade, she helped to stay the Levant’s Mongol menace. The Holy Land, and its sanctified city of Jerusalem, remained in Muslim hands.

Rebuffed by the mosquito in both Europe and the Levant, Kublai sought to counter these setbacks by conquering the last independent vestiges of continental Asia east of the Himalayan Mountains. He set loose the weight of his might on southern China and Southeast Asia, including the powerful Khmer civilization, or Angkor Empire. From its origins around 800, Angkor culture quickly spread across Cambodia, Laos, and Thailand, reaching its zenith at the dawn of the thirteenth century.

Agricultural expansion, poor water management, and climate change provided the mosquito a textbook opportunity to initiate a complete collapse. “Given the reliance on standing impounded water and the breeding of Anopheles,” asserts Dr. R. S. Bray, “the seven delated Me-kong River [was] the source of Khmer prosperity and the source of its malaria”.

The elaborate system of canals and reservoirs used for trade and rice and fish cultivation; extensive clear-cutting and deforestation to increase rice production to feed a growing population; and frequent violent monsoons and flooding created the perfect paradise for the proliferation of mosquito-borne dengue and malaria.

The Me-kong River, with its many canals, was the source of the mosquitos and malaria. (Geo Swan / CC BY-SA 2.0 )

During his southern campaigns beginning in 1285, Kublai disregarded the customary tactic of withdrawing his forces to the nonmalarial north during the summer months. As a result, his marching columns totaling roughly 90,000 men were met by an entrenched mosquito defender. Malaria ravaged his armies throughout southern China and Vietnam, inflicting heavy losses and forcing a complete abandonment of his designs on the region by 1288.

A straggling, sickly force of only 20,000 survivors staggered northward to Mongolia. This retreat from Southeast Asia and the corresponding collapse of the powerful Hindu-Buddhist Khmer civilization were both triggered by the mosquito. By 1400, the Khmer civilization was washed away, leaving only derelicts of awe-inspiring and majestic ruins, including Angkor Wat and Bayon, as reminders of the once flourishing Khmer sophistication and splendor.

Map showing the boundary of 13th century Mongol Empire compared to today's Mongols in Mongolia, Russia, the Central Asian States, and China. (Anchuhu / CC BY-SA 3.0 )

Akin to the Khmer, following its misadventures in southern China and Southeast Asia, the vast Mongol realm corroded, fragmented, and collapsed over the next century, becoming politically and militarily irrelevant by 1400. By this time, political infighting, military losses, and malaria had drained the once invincible Mongol Empire.

Remnants of Mongol provinces lingered until 1500, with one in the backwaters of the Crimean Peninsula and the northern Caucasus limping on until the late eighteenth century. The legacy of the Mongols and of the largest contiguous land empire in history, however, still lives in today’s global DNA.

Top image: Battle between Mongols clans and tribes during the time of Genghis Khan. Source: insima / Adobe Stock.

Excerpted from The Mosquito by Timothy C. Winegard Copyright © 2019 by Timothy C. Winegard. Excerpted by permission of Dutton. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.

By Timothy C. Winegard