Did the Mongols give Europe the Black Death?

Not in the way the famous story tells it, and whether the Mongol world carried the plague west at all is still argued. The famous version says that in 1345-1346 a Mongol army besieging the Genoese port of Caffa, in Crimea, was struck by plague and catapulted infected corpses over the walls, so Genoese ships carried plague to Europe. Caffa really was a thriving Genoese port, set up in 1266 by agreement with the Khan of the Golden Horde, and Jani Beg's Mongols really besieged it, first in 1343. The Black Death arrived in Europe in 1347 and killed up to 50 million people, about 30% to 60% of Europeans.

But the corpse story comes from an Italian notary, Gabriele de Mussis, who was not present, and it is contradicted by contemporary evidence from the Black Sea region. A newer explanation, now widely repeated, is that the plague reached Europe in grain shipments restarted once wartime embargoes were lifted: trade, not a weapon.

Where the plague began is debated. Ancient DNA from graves near Lake Issyk-Kul in Kyrgyzstan with a spike of 'pestilence' in 1338-1339 shows a strain that was the direct ancestor of the Black Death strains. Some scholars think it came from China along the Silk Road with Mongol armies and traders, but that theory is contested: there are no records of Black Death symptoms from Mongol sources before 1346, and the Silk Road was already heavily disrupted.