Mongol invasions and conquests progressed throughout the 13th century, resulting in the vast Mongol Empire, which, by 1300, covered much of Asia and Eastern Europe. Historians regard the Mongol raids and invasions as some of the deadliest conflicts in human history. According to Brian Landers, "One empire in particular exceeded any that had gone before, and crossed from Asia into Europe in an orgy of violence and destruction. The Mongols brought terror to Europe on a scale not seen again until the twentieth century." Diana Lary contends that the Mongol invasions induced population displacement "on a scale never seen before"particularly in Central Asia and eastern Europeadding that "the impending arrival of the Mongol hordes spread terror and panic." In addition, they brought the bubonic plague along with them, deliberately spreading it across much of Asia and Europe and helping cause the massive loss of life in the Black Death. Tsai concludes that "[t]he Mongol conquests shook Eurasia and were of significant influence in world history."