The successful Mongol siege of Kiev in 1240 is generally identified as the final end of the Kievan Rus’ federation, but this is a little too convenient for historical terms. For nearly two centuries, the balance of power in the federation had been shifting gradually from the central authority to the individual principalities, who fought each other for supremacy as much as they fought any external enemies in self-defense. Its ruling Rurik Dynasty began to fragment, as uncles contested with nephews for succession and local princes refused to be governed by the Grand Prince of Kiev. The federation was the kind of political entity whose cohesion depended in large part on the strength of any given Grand Prince, and so when a series of weak (or weakened by infighting) monarchs came to the throne, the federation inevitably came apart.
Then, in the early 13th century, the federation began to suffer heavily due to external challenges. In 1204, the Fourth Crusade sacked Constantinople and drove the Byzantines into exile, which deprived Kiev of its biggest trade partner and “older sister” (the Rus’ had been converted to Orthodox Christianity by emissaries from Constantinople, and Kiev considered itself the heir to Romano-Byzantine culture and society). Kiev’s second-biggest trade partner, the Abbasid Caliphate, was also in steep decline, with the territory that was actually under the caliph’s control having shrunk to Iraq and…well, not much else, and with the Mongols beginning to press on the easternmost parts of the Islamic world. And starting in the 1220s, the Teutonic Knights, another of those Crusades-era religious-military orders like the Knights Templar and the Knights Hospitaller, began to undertake the so-called “Prussian Crusade” against the still-pagan peoples of the Baltic region, which put them right on Kiev’s northwestern border.
So describing the siege of Kiev as the “end” of Kievan Rus’ is kind of a cop out, akin to identifying Odoacer’s conquest of Rome in 476 as the “end” of the Western Roman Empire. It’s not not true, and it is a sort of dramatic punctuation mark on which to hang a basic understanding of events. It’s a clean break point that a high school student can remember, at least long enough to get through the test. But just as Rome hadn’t been “Rome” for quite some time before 476, so Kiev had stopped being “Kiev” well before the Mongols showed up.
The siege of Kiev was the culmination of the Mongols’ second invasion of the Eurasian steppe. In the early 1220s, the Mongol generals Jebe and Subutai undertook one of the most remarkable raids in military history, taking their 20,000-man army into Iran, north through the Caucasus, and back to Mongolia via the northern steppes. Over three years they led their force on a 5500 mile trek around the Caspian Sea, winning victory upon victory in the process. This army fought a Rus’ force of probably around 30,000 (though some estimates go as high as 80,000) at the Battle of the Kalka River in 1223 and almost completely annihilated it. But Jebe and Subutai weren’t there for conquest (and would have had no way to hold on to territory at that time anyway), so they just kept moving until they had returned home.
Owing to the death of Genghis Khan in 1227, the interregnum before he was succeeded by his son Ögedei in 1229, and the need to consolidate gains in China and Iran after that, the Mongols didn’t return to Kievan Rus’ territory until 1235. This time it was an army of conquest, not a raiding party, commanded overall by Genghis Khan’s grandson Batu and in the field by our returning champion, Subutai. The army conquered two Kievan principalities, Vladimir-Suzdal and Ryazan, pretty quickly, then Batu divided his forces into several smaller contingents and sent them after a number of smaller cities. By the 1230s, the Mongols, who initially had no concept of siege warfare (there weren’t exactly a lot of walled cities in the Mongolian-Siberian region), were actually quite skilled at taking cities, owing to their assimilation of Chinese and later Islamic engineering and tactical expertise (and experts–the Mongols had no qualms about, shall we say, coercing people into their service). So they made short work of those smaller cities and towns, then took their time conquering Crimea and parts of what is now western Russia, before training their sights on real prize, the city of Kiev itself.
By this point, the city of Kiev was controlled by the western Kievan principality of Galicia-Volhynia, which had taken it from the eastern principality of Vladimir-Suzdal just a year earlier. Prince Daniel of Galicia sent his most trusted warlord, Dmytro, to defend Kiev, but the Rus’ were heavily outnumbered and the Mongols were well-prepared to take the city. It’s said that the Mongol prince Möngke (who would later become the Great Khan but who for now commanded the advance guard of Batu’s army) sent envoys to Dmytro to negotiate his surrender, because Möngke didn’t want to see such a beautiful city destroyed in a siege, but Dmytro had the envoys put to death. If you know anything about the Mongols, you know that they didn’t appreciate having their envoys killed, so if this really happened then any chance of a peaceful settlement died along with the envoys. After several days of bombardment (the siege began on November 28), the city’s walls were breached and the Mongols burst into the city on December 6.
The Mongols treated Kiev brutally, which is why I’m inclined to think that the thing with the envoys really did happen. However, Mongolian envoys seem to meet with violent ends more frequently than most, which means it’s possible some of these stories are tropes created to explain Mongolian brutality. Either way, they plundered the city of its wealth and burned nearly every one of its buildings to the ground. Of a pre-siege population of about 50,000, it’s believed that only around 2000 survived, though how many were killed during the siege and how many executed afterwards is not clear. Among the survivors was Dmytro, whose bravery impressed Batu even though Dmytro was responsible for putting those envoys to death.
With Kiev down, the Mongols just kept pushing west, invading Poland and Hungary in the 1230s. A succession crisis (really almost a civil war although there wasn’t much fighting), brought on when Ögedei died in 1241 and his son/successor Güyük died in 1248, forced the Mongols to abandon their conquests in those kingdoms and eventually to give up their designs on Europe altogether. Kiev, meanwhile, took centuries to recover from the devastation of the Mongol invasion, which not only destroyed the city (one of the grandest in Europe to that point) but shrunk the population of the Kievan Rus’ territory by a full 1/15th (from 7.5 million to 7 million). That would be the equivalent of over 20 million people dying in the United States today, in case you were wondering.
Even though Kievan Rus’ was coming apart before Kiev was destroyed, the Mongol victory represents the point of no return. From then on, the former federation devolved into its component states. Vladimir-Suzdal was allowed some local autonomy but was made vassal to the Mongolian Golden Horde Khanate. Eventually, one of its cities–Moscow–began to eclipse the others, owing to a very savvy policy of cultivating good relations with its Mongolian overlords. We presumably all know how that turned out. Galicia-Volhynia stayed independent until 1349, when it was divided and absorbed into Poland and Lithuania. A third part, the northern state of Novgorod, remained outside the Mongol sphere, and was independent until its conquest by Moscow in the late 15th century.