The Mithraic Mysteries were a mystery religion practised in the Roman Empire from about the 1st to 4th centuries AD. The name of the Persian god Mithra (proto-Indo-Iranian Mitra), adapted into Greek as Mithras, was linked to a new and distinctive imagery. Writers of the Roman Empire period referred to this mystery religion by phrases which can be anglicized as Mysteries of Mithras or Mysteries of the Persians; modern historians refer to it as Mithraism, or sometimes Roman Mithraism. The mysteries were popular in the Roman military.