Painted in 1358. From the Chronicum Pictum in Hungary's National Library. The dismounted Mongols, with captured women, are on the left, the Hungarians, with one saved woman, on the right.
The Mongols in Hungary 1285 CE.

Cold weather, rain, and flooding stopped the Mongols and saved Europe from the Mongols invincible mounted army in 1242 CE. This, according to an international research team led by Princeton professor Nicola de Cosmo.

None had stood against the Mongol hordes and Europe stood next in line to fall like everyone else. The Polish and Hungarian armies were beaten and Eastern Europe was ripe for harvest, Western Europe was about to be attacked.

Credit: Nature / Ulf Büntgen & Nicola Di Cosmo | doi:10.1038/srep25606
June-August (JJA) temperature variability reconstructed from five regional tree-ring chronologies in Eurasia (~10–90°E and ~45–65°N). Time-series have been normalized (i.e. mean of zero and standard deviation of one) over the last millennium to improve visual comparison, and the vertical bar indicates temperature changes from 1241–1242 CE.

But then the Mongolian army suddenly stopped their advance into Europe, turned around and headed back home in the winter of 1242.

Cosmo and his team present a hypothesis that the weather was the reason to why the usually victorious Mongol leader Batu Khan retreated.

Quagmire Broke the Mongols

The scientists made a dendroclimatic study of growth rings in trees. These indicate that the winter of 1242 was particularly cold and wet in Central Europe.

Open grass plains were fundamental for the logistics of such a large army on horses. Since this weather possibly turned the central European plains into a quagmire – it made the terrain difficult to traverse for the Mongol mounted forces.

This unusual weather is also mentioned in written historical sources. They testify about a historical flooding of the The Great Hungarian Plain. Which most probably hampered the nearly 130,000 Mongol warriors and their horses, being unable to graze. Ensuring sufficient grazing for the massive horse herd was crucial.

Therefore, the researchers believe that the Mongols made their way to the greener pastures of Russia instead.

Ögedei Khan Died

Credit: Nature / Ulf Büntgen & Nicola Di Cosmo | doi:10.1038/srep25606
Spatiotemporal characteristics of the Mongol invasion of and sudden withdrawal from Hungary between 1241 and 1242 CE.

Other historians have long pointed out that Batu Khan probably interrupted his campaign because of the great Khan Ögedei’s death in December 1241 CE.

This explanation is not enough, though, according to Nicola de Cosmo, who is referring to the fact that Batu Khan never returned home to the Mongol capital of Karakorum to participate in the election of a new great khan.

“The weather was certainly not the only reason for the retreat, but to ignore it is like saying that the Russian winter had no effect on Napoleon’s army,” says Professor of Cosmo.

Climatic and environmental aspects of the Mongol withdrawal from Hungary in 1242 CE