long sword used by Celtic auxiliaries in the Roman army during the first century CE. The spatha gradually became a standard heavy weapon used by Roman infantry in the third century CE.

A pair of metal detectorists bundled up and headed into a snowy forest in Poland. They hoped to find some artifacts from World War II — yet stumbled upon a much older and rarer weapon.

Proszowski and Lampa reported the find to archaeological officials, who tentatively identified it as a Roman spatha, a characteristic long sword used by horsemen, officials said. The weapon ...