War explores how the Silk Road influenced conflict, from cavalry warfare to gunpowder. The series opens 2000 years ago, when the Roman Empire seemed unstoppable. However, the Battle of Carrhae saw one of Rome’s worst military defeats when the Parthians used cavalry tactics to their advantage. The style of cavalry warfare developed by Central Asian horse archers would later dominate warfare, made possible by several innovations; the recurved composite bow, socketed bronze arrowheads and a psychological shift towards cohesive groups of soldiers under military command. It was also around this time that the Roman Empire began to covet Chinese silk. Long distance trade between the peoples of Eurasia was nothing new; for thousands of years, similar relations had been impacting societies.