In 1861, an archaeologist named James Farrer broke into a grass-covered Neolithic tomb on the Orkney Islands expecting to find ancient bones and treasure. The tomb was empty. But its walls were covered with runic inscriptions, dozens of them, carved by Norse visitors centuries earlier. Most were mundane: "Arnfinnr Food carved these runes." Some were lewd: Two were extraordinary: "Crusaders broke into this barrow." "Jerusalem-men broke this mound." The worlds of the Viking north and the Crusades are artificially separated in the popular imagination, but Scandinavians were among the most enthusiastic, brutal, and consequential crusaders in history – working as the shock troops of the first four crusades, and single-handedly converting pagan Baltic Europe to Christianity in a couple of centuries.

Today's guest is Thomas Williams, former curator at the British Museum and author of God's Hammer: A History of the Viking Crusades. We discuss how Scandinavians went from being Christianity's most terrifying enemies to some of its most enthusiastic holy warriors within two centuries, why Harald Hardrada served as a Byzantine mercenary across the Mediterranean and may have policed the pilgrimage routes to Jerusalem sixty years before the First Crusade, and how Vladimir of Kyiv chose Byzantine Christianity over Islam partly because "drinking is the joy of the Russes." We look at how the Norwegian King Sigurd fought his way through the entire Mediterranean six years after the First Crusade to help capture the port of Sidon and received a splinter of the True Cross, and why the Danish conquest of a pagan temple fortress on the Baltic island of Rügen established the template for centuries of northern holy war. Williams argues that crusading gave the violence that had always defined Norse culture a new legitimacy and a new set of enemies, and that they had found a way to be Vikings and Christians at the same time.