The crucifixion of Jesus gives birth to global religion, but Christianity may never have happened without the Roman Empire. The Roman Empire's vast network of roads and shipping lanes allows goods and ideas to flow across three continents, allowing Jesus' message to transform Mankind around the world. When Rome is sacked by barbarians, Europe enters a Dark Age. But from the fringes of the old empire, two new forces remake the world. The Arabs, funded by a gold rush, unite under the banner of Islam. The Vikings rejuvenate the cities of Europe, travel to America and become Christian knights. The stage is set for a clash of civilizations--the Crusades.