In Roman Conquest and Expansion, archaeologist and historian Richard Miles explain how Rome’s legionary army became the backbone and driver of its expansion. As Rome conquered more and more groups and land, they grew their army and their empire. Eventually, they transformed Rome from a small city-state to a dominant power. This video is excerpted from BBC’s Ancient Worlds, an epic series with archaeologist and historian Richard Miles as he explores the roots of civilization from Mesopotamia to the fall of the Roman Empire.

In Ivan the Terrible and Siberian Expansion, host Andrew Marr describes the Russia of the past as a poor country until a dip in global temperatures drove up the prices and the demand for fur pelts. Russian mercenaries ventured into Siberia where their superior European weapons helped them defeat local forces. This video is excerpted from BBC’s Andrew Marr's History of the World, a story of human history that uses reenactments, modern footage, and storytelling to explain history’s greatest achievements.