From its northernmost tip to the border with Asia, plenty of ancient European armies were happy to welcome women to their ranks. Traditionally, though, historians have agreed on one major exception to this rule: the Roman Empire, where the army and navy were – almost by definition – made up only of men. 

According to a recent paper, that was a really poor decision on the Romans’ part – not least because they knew exactly how ferocious women could be on and off the battlefield.