"Yersinia pestis" has been discovered in archaeological finds from the Late Bronze Age (~3800 BP). The first recorded epidemic affected the Sassanian Empire and their arch-rivals, the Eastern Roman Empire (Byzantine Empire) and was named the Plague of Justinian after emperor Justinian I, who was infected but survived through extensive treatment. The pandemic resulted in the deaths of an estimated 25 million (6th century outbreak) to 50 million people (two centuries of recurrence). The historian Procopius wrote, in Volume II of History of the Wars, of his personal encounter with the plague and the effect it had on the rising empire. In the spring of 542, the plague arrived in Constantinople, working its way from port city to port city and spreading around the Mediterranean Sea, later migrating inland eastward into Asia Minor and west into Greece and Italy. Because the infectious disease spread inland by the transferring of merchandise through Justinian's efforts in acquiring luxurious goods of the time and exporting supplies, his capital became the leading exporter of the bubonic plague. Procopius, in his work "Secret History", declared that Justinian was a demon of an emperor who either created the plague himself or was being punished for his sinfulness. In the Late Middle Ages Europe experienced the deadliest disease outbreak in history when the Black Death, the infamous pandemic of bubonic plague, hit in 1347, killing a third of the European human population. Some historians believe that society subsequently became more violent as the mass mortality rate cheapened life and thus increased warfare, crime, popular revolt, waves of flagellants, and persecution. The Black Death originated in Central Asia and spread from Italy and then throughout other European countries. Arab historians Ibn Al-Wardni and Almaqrizi believed the Black Death originated in Mongolia. Chinese records also showed a huge outbreak in Mongolia in the early 1330s. Research published in 2002 suggests that it began in early 1346 in the steppe region, where a plague reservoir stretches from the northwestern shore of the Caspian Sea into southern Russia. The Mongols had cut off the trade route, the Silk Road, between China and Europe which halted the spread of the Black Death from eastern Russia to Western Europe. The epidemic began with an attack that Mongols launched on the Italian merchants' last trading station in the region, Caffa in the Crimea. In late 1346, plague broke out among the besiegers and from them penetrated into the town. The Mongol forces catapulted plague infected corpses into Caffa as a form of attack one of the first known instances of biological warfare When spring arrived, the Italian merchants fled on their ships, unknowingly carrying the Black Death.