Back in the first millennium A.D., waves of human migration across Europe created an elaborate genetic puzzle that researchers have now started to unravel with a leap in DNA analysis. An enhanced look ...

9 B.C.: Pagan Germanic tribes check advancing Romans in the Battle of the Teutoburg Forest, ending northward spread of Roman civilization, bounding the Roman Empire by the Danube and Rhine. c.700 A.D.

Fortified by forts and watchtowers, the 1,700-mile river formed the empire's northern border, with Rome on one side and Germanic tribes on the other. The Great Ludovisi sarcophagus depicts the chaos ...