Paul Freedman, professor at Yale, traces how Christianity became the Roman Empire's official religion, centering on Constantine's conversion after the Battle of the Milvian Bridge in 312. He argues that embracing Christianity looked like poor political strategy given how sharply it clashed with Roman values, yet it became a masterstroke that reshaped both empire and church. The lecture follows Constantine's rise to power, his new role as a Christian emperor intervening directly in church doctrine, and his founding of Constantinople, a new capital in the East that raised the possibility of a Roman Empire without Rome itself. Freedman closes by comparing Constantine's methods and legacy with those of his predecessor Diocletian. Part of Yale's Early Middle Ages course, the talk moves chronologically through chaptered sections covering Constantine's ascent, conversion, religious policy, and new capital.