Although not specifically used as a spear tactic, the siege of Caffa immediately springs to mind. In 1346 the mongol tribes were making their way across Europe, under Jani Beg and had begun a lengthy siege at the city of Caffa. Running out of artillery and his troops being ravaged by disease, Beg took the decision to launch the bodies of the dead into the city in order to infect those inside and weaken their resolve. The disease in question was none other than the Black Death. An historian Le believe this to be the first known act of biological warfare. Ultimately Beg lost too many troops and was forced to withdraw but he had unwittingly set in motion one of the greatest plagues in history as refugees from Caffa fled westward deeper into Europe spreading the plague as they went. The Black Death has been estimated to have killed between 30-60% of the population of Europe at the time.