How climate forced the Mongols to leave Hungary in 1242

The Mongol Empire in the 13^th century was the largest contiguous land empire ever. At its westernmost expansion into Europe, the sudden withdrawal of the Mongols from Hungary in 1242 CE still generates much speculation. Researchers from Switzerland and the US present a new ‘environmental theory’ to this long-debated mystery. Their study, published today in Nature Scientific Reports, shows how minor environmental fluctuations can influence major historical events.

Although there is increasing awareness of the role that climate played in human history, it is evident that paleo-environmental insights must be supplemented with multifactor analyses to overcome deterministic, reductionist or monocausal explanations. The Mongol invasion of Eastern Europe, and especially the sudden withdrawal of Mongol armies from Hungary in 1242 CE, provides a fitting case study to further enhance the appreciation of environmental conditions under which historical events may have occurred.

Nicola Di Cosmo, an experts in East Asian History at the Institute for Advanced Study in Princeton, USA, and Ulf Büntgen a tree-ring specialist at the Swiss Federal Research Institute WSL in Birmensdorf compiled and investigated available documentary sources and tree-ring chronologies between 1230 and 1250 CE. This unique dataset indicates that warm and dry summers from 1238-1241 were followed by cold and wet conditions in early 1242.

Army stuck in mud

The authors suggest that marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility, as well as the military effectiveness of the Mongol cavalry, while local despoliation and depopulation ostensibly contributed to widespread famine. These circumstances arguably contributed to the Mongol commanders’ determination to abandon Hungary and return to Russia.

“This case study proves the critical role of environmental factors in the study of premodern societies, and it is of particular importance in the study of macroscopic events such as the formation of the Mongol empire. Historians may have underestimated not only the challenges met by the Mongols as they expanded across different ecological zones, but also the effects of climate variability upon the operations of the Mongol armies. These effects can only be assessed precisely through the collection and analysis of climate data from natural archives.” states Di Cosmo.

Lessons from the past

The interdisciplinary approach clearly expands beyond all one-dimensional and/or multi-disciplinary studies that were previously dedicated to the Mongols. Moreover, this study advocates for an entirely new form of investigation that combines palaeoclimatic reconstructions with documentary sources in relation to short-term historical events. Thanks to his dendroecological background, Büntgen can refer to absolutely dated, annually resolved and spatially explicit proxy archives. He concludes that “regardless of the different driving forces involved, consideration of the complexity of various direct and indirect relationships between environmental factors and historical events might prove instructive when pondering linkages between climate and human behavior, especially in the light of present-day issues involving war and migration.”

By introducing an ‘environmental theory’ to explain the sudden withdrawal of the Mongols from Hungary in 1242, the authors now offer a new solution to a contentious historical question. In so doing, they demonstrate that even minor climatic fluctuations and short-term environmental changes may play a decisive role in constraining societal action and affecting decision-making in strategic context.