Genghis Khan led the rise of the Mongol empire in Europe, with his loyal hordes sweeping one territory after the other.

They successfully pillaged cities in Poland and Hungary, extending their reach from the East. But just as they were setting their sights on Austria, the ferocious Mongol warriors retreated back to Asia in 1242.

Indeed, the gradual rise of the Mongol empire ended abruptly. What could have caused its downfall?

Rewinding History

During the early 13th century, the Mongols' thirst for warfare and bloodlust emerged under the leadership of Genghis Khan. His son Ögödei and grandson Batu continued the succession. By 1279, the Mongol empire encompassed swathes of land in Eurasia, China, Russia, Iran, and Central Asia.

Backtrack a few decades. In 1230, the Mongols were still establishing their rule over Russia, producing what would be now known as the Golden Horde. By 1240, the hordes expanded into Eastern Europe. Thanks to a sophisticated military coordination, the Mongols crushed the Polish and the Hungarians.

But in 1242, they crossed the Danube River, wreaked havoc for weeks, then retreated through Siberia and Bulgaria back to Russia. Why?

According to a new published report in the journal Scientific Reports, a multitude of factors contributed to the sudden withdrawal, but the most central aspect that triggered it was environmental fluctuations.

Yes, the Mongols were defeated in part by bad weather, and the rest of Europe was spared.

Authors of the study investigated countless documentary evidence and paleoclimactic analysis, focusing on tree-ring chronologies.

Written evidence suggests that the spring of 1241 was warm. Stocks of food were plentiful for both troops and horses. Little did they know that winter was coming.

The frigid conditions struck early and with vigor. The Danube River froze over, becoming a bridge for Mongol armies.

As the coming year melted into spring, the sudden accumulation of ice and snow caused flooding, turning solid ground into marshland. This hindered the military strategy of the Mongols and triggered the onset of famine.

And like the Dothraki, the Mongols relied on their horses greatly. When they ventured into areas where the climate was not suitable for horses, the mighty Mongols began to falter.

Again, the authors of the report noted that there was enough pasture to support the herds of the Mongols. These invaders left crops and land intact as they invaded Hungary.

But much of the soil in Hungary was prone to ponding and stagnant moisture, researchers said.

Add that to the brutal winter, the early arrival of spring, and the following thaw and snowmelt — the Mongols experienced a tumultuous set of conditions that dramatically reduced their land for grazing.

The ravages of war and the fluctuating climate conditions contributed to failed harvest and the great famine in Hungary. Food supplies were reduced for soldiers and civilians alike.

Singing Praises

Professor Aaron Putnam of University of Maine, who was not involved in the study, said using one environmental factor to explain reasons behind historical events is always tricky.

Still, Putnam praised the authors of the report as they made a good job of presenting a solid chronological case that climate deterioration played a key role in the abandonment of Mongols of the Hungarian Plains.

Meanwhile, the authors of the study emphasized that it was not the specifics of the Mongol retreat that were important, but the principle it brings to light. Perhaps, there is more we can learn from history than we know.