 Once-vassal dynasties in Armenia, Cappadocia, and Pontus were threatening Syria and northern Mesopotamia; the nomadic Parthians, brilliantly led by Mithridates I of Parthia, had overrun upland Media (home of the famed Nisean horse herd); and Roman intervention was an ever-present threat.Sidetes managed to bring the Maccabees to heel and frighten the Anatolian dynasts into a temporary submission; then, in 133, he turned east with the full might of the Royal Army (supported by a body of Jews under the Hasmonean prince, John Hyrcanus) to drive back the Parthians.Sidetes' campaign initially met with spectacular success, recapturing Mesopotamia, Babylonia, and Media.