Notes: Part Two can be found here. "The Scythians were an ancient Iranic people of horse-riding nomadic pastoralists who, throughout classical antiquity, dominated the Pontic-Caspian steppe, known at the time as Scythia," according to the Ancient History Encyclopedia. Their history is murky and it's unclear if the Scythians were even a distinct people, but they are thought to have originated somewhere in the region between the Black Sea and southern Siberia/central Asia.
"Scythia" was "the broad term used by Greeks and Romans to characterize the lands to their north and east, roughly from the Danube to the Don, Caucasus and Volga," according to the Oxford Classical Dictionary (OCD, 3rd ed. revised). "The history of Scythia resists construction" and they were apparently first mentioned by Herodotus in the 8th century BC.
According to the OCD, "there is a very broad consensus on the course of Scythian history from the early 7th cent. [BC] when, as Herodotus would have it, Scythians forced the Cimmerians southwards across the Black Sea and themselves campaigned deep through the near east."