Rome's power was built not only on production, but on relentless expansion that fed its system with the wealth of conquered worlds. Scipio Africanus broke Carthage and seized North Africa; Pompey the Great absorbed the riches of Asia Minor and Syria; Julius Caesar swept through Gaul, hauling back land, silver, and enslaved laborers by the hundred thousand.

Yet what flowed in could also flow out. Roman elites poured fortunes into imported luxuries — papyrus from Egypt, carpets and perfumes from Parthia, silk and spices from the East — draining silver eastward year after year and slowly debasing the empire's coinage. Under Trajan, a Roman merchant named Maes Titianus pushed a caravan deep into Central Asia, determined to bypass Parthian and Kushan middlemen and reach Han China at the source.