Mongols Attacked And The Earth Fought Back)

At their peak, the Mongols were a formidable force. With very few exceptions, they succeeded in taking over everywhere they attacked, forming the largest continuous land empire in human history. So what was powerful enough to make the Mongols retreat? Well, turns out, the Earth itself. The few times they were defeated tended to have one thing in common, weird weather. Scientists have reconstructed these events to answer questions that have nagged historians for centuries. From typhoons to the Little Ice Age, here's the lousy weather that brought down the mighty Mongols. In the 13th century, the Mongols began a massive westward expansion from their capital in Mongolia. Starting under the command of Genghis Khan and continuing with his son Ogedei and grandson Batu, they conquered parts of what are now China, Russia, and Iran. Their conquests reached across what's now called the Grassland Highway, a strip of grassy plains that stretches across Eurasia, ending in Hungary. And in 1241, the Hungarian king did what I'd probably do if I were invaded by 130,000 soldiers of a notorious army. He fled. Then Batu Khan got to work setting up the foundations of an occupying government. It was looking like an inevitable expansion of the empire. But the next year, the Mongols abruptly turned around and retreated. For centuries, historians have wondered what caused this change of heart. Nearly 800 years later, paleoclimatologists have finally found clues to the mystery in the trees. If you count a tree's rings, you can figure out how old it is. But because a new ring grows each year, they can also record information about the conditions, like how warm it was that year. These researchers looked at trees from five sites across Europe that revealed four years of warm summers starting in 1238. But this balmy spell abruptly ended with a particularly cold and wet 1242. Historical accounts indicate the Mongols had difficulty crossing flooded and muddy terrain. I mean, I don't know if you've ever tried to operate siege engines in the middle of a muddy swamp. Apparently, it's no piece of cake. On top of that, the combination of war and cold weather led to a famine in Hungary. Each Mongol soldier would travel with about five horses. That's a lot of mouths to feed. They relied on the bounty of the lands they conquered to feed them all. But flooded grasslands would have left less area for the horses to graze. So the researchers think this shift in weather literally caused the Mongols to get stuck in the mud and forced them to retreat. Now, it's important to note this is a hypothesis, and one that certainly not everyone agrees with. But Hungary's history might look very different if it weren't for Mother Earth's muddy intervention. And something similar happened the next decade. In 1258, 120,000 Mongols pushed into Syria, only to retreat two years later. And as with their trouble in Hungary, it has always been kind of a mystery why. But their fate might have been sealed before the attack ever began. See, a year earlier, the Samalas volcano erupted in Indonesia. I know, Indonesia is a long way away from Syria. But this story gets even weirder. To make the connection between the two things, researchers had to travel to Greenland and Antarctica to extract long samples of ice. They were looking at the ice in cold places, where it's preserved in layers that identify exactly when it froze into place. And in the ice layer from 1257, they found abnormally high amounts of sulfate, one of the big things that volcanoes spit into the air when they erupt. From this data, we know that the eruption of the Samalas volcano was the largest in 2,500 years. Which means that sulfate would have traveled far and wide. These ice cores were solid evidence of just that. Eruptions of this size spew tiny aerosol particles into the atmosphere, which not only get trapped in ice for thousands of years, but also have the more immediate effect of reflecting some of the incoming sunlight. This means less heat from the sun gets absorbed by the earth and atmosphere. And it can have a big impact on the climate. The same research team that studied the Mongols' time in Hungary looked at more tree rings and used a computer climate simulation to figure out the volcano's impact on the Syrian climate after this eruption. They found that immediately afterward, the summers became cooler and much wetter for a few years. Here, they think the rain was temporarily a good thing, because it increased the greenery of the region, feeding all those hungry Mongol soldiers and horses. That's hungry, like the feeling. Not hungry, like the country. But when things reverted to the pre-eruption dry conditions in 1260, the land couldn't support an army large enough to defend the Mongols' new territory. This idea matches another study that found that back in central Mongolia, the initial conquests of Genghis Khan correlated with the warmest and wettest period in the last thousand years. These were times when favorable weather provided lots of productive grasslands for large herds of livestock. So it appears that the eruption made Syria seem like a great place to invade until it reverted to a desert. But as we've already seen, you can have too much water, and that's what happened to Mongols again in one of their most famous attacks. But before we get to that, here's a quick ad. This episode of SciShow is supported by MantaSleep. MantaSleep makes sleep masks and sleep accessories designed to help you get the energy to create your best life. To get a 15% off deal on all of that stuff, you can head to the link in the description. The people at MantaSleep are well aware of the afternoon slump when you feel low on energy, focus, strength, and clarity. But instead of pushing through and letting their performance suffer because of it, they have ideas to combat it. Like using their ProSleep mask for afternoon naps. The mask is adjustable and feels like what you thought a cloud felt like when you were a child. For 15% off your MantaSleep masks and accessories and a free holiday recharge kit, check out the link in the description and use the code SCISHOW. 14 years after their attack in the Middle East, the Mongols set their sights on Japan. But it proved harder to get to than they anticipated. Twice, Mongol fleets attempting to invade the island were crushed by kamikaze storms, which translates to divine wind. And they got that name for a good reason. In November 1274, Kublai Khan attacked Japan with 30,000 soldiers in hundreds of boats. But a third of the boats were destroyed by a massive storm that swept through, killing 13,000 of his army. So in August 1281, he sent even more, this time as many as 200,000 soldiers in thousands of boats sailed for Japan. But another typhoon approached, so the fleet had to shelter in Amari Bay. There was still no match for the ferocious storm. Half the soldiers died, and today, archaeologists find weapons and splintered remains of ships on the seafloor. Historians have found this astonishing, because the probability of two such events occurring at the right time and place to destroy both fleets is extremely low. Typhoons are rare in November, when the first fleet was hit, and also rare in Amari Bay, where the second fleet was sheltering. So in a 2014 study, geologists pulled a sediment core to see if they could find evidence of these storms. This time, they took their core from the bottom of a coastal lake in Japan. In this peaceful lake, sediment layers accumulate gradually every year, except when there's a typhoon, which washes denser material from the nearby beach into the lake and forms a recognizable layer at the bottom. The radiocarbon dates in the core aren't precise enough to be sure which layers are the exact storms from 1274 and 1281. However, they can see that this was a period of more frequent strong typhoons than we see today. So they think there's a high probability that two of these typhoon layers are from the Kamikaze storms that pushed back the Mongols. It's yet another case of foul weather defeating an otherwise invincible army. But we still have one last example to cover. Between 1330 and 1390, the Mongol Empire started to decline, even in their longtime stronghold of China. This is known as the Chinggisid Crisis. Now, there were a lot of reasons for this. Political instability and the spread of the Black Death are the most commonly cited, but there was also evidence that climate change played a role. This was the beginning of the Little Ice Age, 500 years of particularly variable and chilly temperatures. Besides more tree ring studies, paleoclimatologists have used pollen, stalagmites, and even bat poop, or guano, to show how important climate was during this period. Looking at which types of pollen are preserved in peat bogs tells you what plants were thriving each year. The chemical composition of stalagmites growing up from the cave floors records how much rain fell in a year. And speaking of cave floors, bat guano gives you an idea of what bats were eating during a certain period. Combining these lines of evidence with historical documents, scientists believe that the start of the Little Ice Age in China was a rollercoaster of climate. Periods of heavy rainfall and flooding alternated with intense drought. This led to crops failing and plagues of locusts, which further decimated the food supply. The famines of the 1340s were so bad, there are even reports of cannibalism. The Mongol government responded by spending as much as 30% of their budget on aid for the population. But this depleted their coffers and devalued their currency. All of this led to social unrest and rebellions. The Mongols finally lost control of China in 1368, when Ming forces pushed them out. The Mongols had a good run, but even the largest land empire in human history wasn't impervious to the weather. So next time you're planning an empire-expanding campaign in a far-off land, you might want to check the long-term forecast first.