A pair of researchers has found a possible explanation for the sudden, mysterious reason that the Mongol army withdrew from Eastern Europe in 1242, just when it seemed poised to take Hungary. In their paper published in the journal Nature, Ulf Büntgen with the Swiss Federal Research Institute and Nicola Di Cosmo with the Institute for Advanced Study in the U.S. describe a study they made of tree ring data from trees in Hungary and historical records, which showed that the weather during the time of the Mongol invasion was not particularly well suited for an army traveling on horseback.
For hundreds of years, historical scholars have puzzled over the sudden retreat by the Mongols—they had conquered their way out of Asia and into Russia and had won every battle they had fought making their way into Eastern Europe during the early 1200s, when they abruptly turned tail and headed back to Russia, never to return. Some have suggested it was Mongol politics while others have maintained that armies in the Eastern Europe were putting up much more of a fight than the Mongols had expected. In this new effort, the researchers suggest that the reason might be much more mundane: simple bad weather.
The horses used by the Mongols, the researchers note, survived by eating the grasses that were plentiful on the Asian and Russian steppes—grasses that were healthy and strong and easily accessible due to several years of good weather. But, tree ring data, and some evidence in historical writings suggest that the winter of 1242, was particularly bad—not because it was too cold, or too snowy, but because it was just cold enough to cause widespread freezing which led to widespread melting during the spring, which just happened to coincide with the arrival of the Mongols. The melting led to flooding, because, coincidently, that part of Hungary sits at low elevations—melting ice and snow would have puddled, preventing the grass for growing very well that spring, leaving little for the horses to eat. Also, it would have meant lots of mud, making travel very difficult. The end result, the researchers suggest, might have been the Mongols simply deciding against progressing further because it did not seem worth the trouble.
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Ulf Büntgen et al. Climatic and environmental aspects of the Mongol withdrawal from Hungary in 1242 CE, Scientific Reports (2016). DOI: 10.1038/srep25606