In the Roman Empire, newborn babies were wrapped in strips of cloth for around two months. Their limbs would gradually be released, starting with the right arm, so the baby would get used to using it. Being left-handed was seen as a very bad omen, and left-handed Romans were considered unlucky and untrustworthy. And you certainly couldn’t be a left-handed soldier, as a carefully-crafted Roman battle formation would fall apart unless everyone was moving in lockstep with their weapons in exactly the same hand.