The Jurchens were a nomadic people, originally from the far east, who in the 13th and 14th Centuries migrated westward all the way to Europe, appearing in force on the steppes north of the Danube where they displaced earlier tribes and posed a threat to the Byzantine Empire on the river's south bank. The Byzantines did not know (and did not greatly care) what had driven the Jurchens from their original home and made them migrate so far west. What mattered was that they were a dynamic and capable people who presented an increasing threat to the Empire.