On a fortified hill in Scotland some 1,900 years ago, a Roman army attacked local warriors by hurling lead bullets from slings that had nearly the stopping power of a modern .44 magnum handgun, according to recent experiments.

The assault seems to have been deadly effective, for the local warriors were armed only with swords and other simple weapons, says John Reid, a researcher at the Trimontium Trust and one of the co-directors of the archaeological fieldwork at Burnswark, south of Edinburgh. “We’re fairly sure that the natives on top of the hill weren’t allowed to survive.”

But Burnswark was just the opening salvo in a war against the restive tribes living north of Hadrian’s Wall. Despite their superior weaponry, Roman