In four years, Genghis Khan had trampled the Muslim East that is now Kazakhstan, Uzbekistan, Afghanistan, and Pakistan. His armies then ran into a serious problem: as they came out of the mountain and steppe country, heat and humidity made their bows shoot inaccurately. Even in winter, it just wasn’t working. The Khan decided to take the main army, two tumens, back to Mongolia in 1222. (Captives from conquered cities cleared the mountain passes of snow for them, since their lives were not worth anything.)
The other two tumens were sent farther west, probably in pursuit of the Shah of Khwarismia, who had fled. They invaded Armenia and Georgia, coming into official Christendom. Georgia became a vassal state of the Mongols after one devastating battle. For the first time, the Mongols began to have some notion of what was on the other end of the Silk Road. The tumens then moved north, where they encountered the Kievan Rus. Ten envoys approached the Kievan princes to learn what sort of relations the Mongols could expect: alliance or surrender? The envoys were executed. Clearly, the Rus had not heard about the fate of Khwarismia, that did the same, or they thought they’d be different.
It’s worth looking at Jack Weatherford’s account of the Battle of Kalka River in Genghis Khan and the Making of the Modern World. The battle wasn’t a significant turning point for the Mongol campaign, but it illustrates the Mongols’ idiosyncratic ways of fighting that so baffled Europe and the Middle East.
First, the Mongols began a long retreat that lasted for days; the Slavic cavalry and foot soldiers followed them, thinking that “chasing means winning.” Because the Mongols were on horseback, they could set the pace so as to string out and thin their enemies over many miles. When they suddenly turned to fight, the Rus had no plan for retreat, supply or reinforcement. The Mongols got to choose the fighting venue, on the plain where the Kalka River empties into the Sea of Azov.
The Russians fought as European wars had taught everyone to do: in close formation, in lines that must not break. But the Mongols didn’t attack them at first. They played drums, then suddenly became quiet. Then they began an unusual form of assault that was coordinated with signal flags. Their horses charged, but as the Slavs braced for the clash, the Mongols pulled up. They began firing volleys of arrows at close range, staying out of reach of hand combat. To the Mongols, the Rus were conveniently bunching together like a herd of buffalo. It was easy hunting.
The Slavs had bowmen, but their bows were not as powerful, so when they fired back, the Mongols could ride out of range. Worse, the Mongols fired Russian arrows back at them. They had examined western bows and found a way to make Mongolian arrows not compatible with Russian bows, while Mongolian bows easily used Russian arrows. The foot soldiers of the Rus stampeded into a retreat, which made them run into other troops still arriving, and they crowded and tangled the mounted knights. The Mongols followed, picking off peasants and princes. The Novgorod Chronicle, says Weatherford, reported that only one in ten Slav survived to reach home.
The Mongol army camped in Crimea to rest for some weeks, and they executed their captive princes in a Mongol fashion: rolling each one in felt, they built a wooden platform on top of them and crowded in for a banquet. They were honoring their rank by not spilling blood, but punishing them for executing ambassadors.
Since we know that the Mongols trashed the Russian heartland, we’d expect that this is when they did it. But they didn’t. There was a general movement among the Mongols to stop expanding for now, to pull back and see what would happen next. They may also have been having the same problem with humidity and bows near Kiev as they’d had in Pakistan. So in the summer of 1223, the western Mongol army headed for home, looping back by a more northerly route to find dry grasslands faster and keep scouting new land.