According to the Gabriele de Mussi the Golden horde indeed had lobbed plague-infested corpses into the Genovese-controlled Kaffa in Crimea in 1346.
“The dying Tartars, stunned and stupefied by the immensity of the disaster brought about by the disease, and realizing that they had no hope of escape, lost interest in the siege. But they ordered corpses to be placed in catapults and lobbed into the city in the hope that the intolerable stench would kill everyone inside. What seemed like mountains of dead were thrown into the city, and the Christians could not hide or flee or escape from them, although they dumped as many bodies as they could into the sea. As soon as the rotting corpses tainted the air and poisoned the water supply, and the stench was so overwhelming that hardly one in several thousand was in a position to flee the remains of the Tartar army. Moreover one infected man could carry the poison to others, and infect people and places with the disease by look alone. No one knew, or could discover, a means of defense.”
This is how he explains the black plague in Europe.
“among those who escaped from Caffa by boat were a few sailors who had been infected with the poisonous disease. Some boats were bound for Genoa, others for Venice, and to other Christian areas. When sailors reached these places and mixed with people there, it was as if they had brought evil spirits with them: every city, every settlement, and their inhabitants, both men and women, died suddenly.”
Is his narrative legit? Well, we know from other sources it were Genovese merchants who brought the disease first to Sicily and to Marseilles. But where did they catch it?
“We Genoese and Venetians bear responsibility for revealing the judgements of God. Alas, once our ships had brought us to port we went to our homes. And because we had long been delayed by tragic events, and because among us there were scarcely ten survivors from a thousand sailors, relations, kinsmen and neighbors flocked to us from all sides. But, to our anguish, we were carrying darts of death. While they hugged and kissed us we were spreading poison from our lips even as we spoke.”
In 1332 some contagious disease killed the emperor of China and wiped out the population of Huebei. In 1341 there was an outbreak in Samarkand. By 1347 it was in Constantinople and Sicily. In 1348 in Italy, France, Spain and England. In 1349 in Germany. The Siege of Caffa in 1346 as a turning point sounds legit but it might as well have gone naturally through all the trading hubs in Asia.