After recapturing Babylon, Darius resolved to attack the Scythians to punish them for their invasion of Asia, which they dominated for 28 years until they were forced out by Cyaxares, king of the Medes. Book 4 describes Darius’ campaign in Scythia and gives an account of the geography and peoples of northern Europe. In the second half of the Book, Herodotus relates the Persian invasion of Libya and provides a brief description of the Libyan tribes and topography, as well as an account of the founding of the Greek city of Cyrene on the Libyan coast.

The Scythians claim to be the youngest of all nations, tracing their lineage back 1,000 years to their first king, Targitaus. Herodotus believes the Scythians were nomads who originally lived in Asia until they were forced northward by the Cimmerians and came to occupy the territory north of the present-day Crimean Peninsula on the Black Sea. Herodotus describes the variegated geography of the region and the several tribes of its Scythian and other inhabitants. Nothing is known about the areas north and east because a high mountain range blocks access. Reportedly, goat-footed men live on the mountains and beyond them are inhabitants who sleep six months of the year, but Herodotus rejects these stories.