• The Emperor Trajan made careful preparations to invade Parthia between 111-114 CE.
• In 115 CE, he invaded and captured the Parthian capital, Ctesiphon and added Mesopotamia as a Roman Province. This expanded the Roman Empire to its greatest extent in its history.

The Reason for the War

• The Romans dreamt of repeating Alexander the Great‘s domination of the East.

Preparations for the War with Parthia (111-114 CE)

• Letters between Pliny the Younger and Trajan show that Trajan had already been preparing and provisioning ten Legions in the East as early as 111 CE, although no new Legions were created for this War.
• In 112 CE he promoted the future Emperor, Hadrian, Commander in the East, based at Antioch in Syria.
• For 50 years the Roman and Parthian Empires had shared appointing the Kings of Armenia.
• In 113 CE, when Parthia didn’t consult Trajan, and appointed their own choice of King, Trajan declared War.
• This was to make Trajan, the first Roman Emperor to invade Parthia.

The Invasion of Armenia (114 CE)

• In 114 CE, Trajan collected the Eastern Legions as he moved out of Antioch, he was joined by an additional 2 Legions from the Danube, and various Vexillatios from other Legions, giving him around 80,000 men.
• Trajan then invaded Armenia, the eastern part of modern Turkey, where he replaced the Parthian appointed King.
• Trajan continued the campaign and the surrounding Kingdoms fell or surrendered to the Roman Armies.

• Trajan’s strategy was to be a pincer movement launched from Armenia:
  1. One Roman Army was to go north under Lucius Quietus, across the River Araxes from Armenia, and invade the area between the Caspian Sea and the Caucasus. This would divide the Persian Army.
  2. Trajan then split the remaining Legions into two groups.

The Invasion of Mesopotamia (115 CE)

• In 115 CE Trajan invaded Mesopotamia:
• One army headed east and then down towards Babylon.
• Whilst Trajan, starting from Dura Europos on the Euphrates, had a fleet of 50 ships built. These he sailed down the Euphrates.
• Trajan then portaged (hauled) his ships over a 20 mile strip of land between the Euphrates and the Tigris.
• Once on the Tigris, he captured Seleucia and the Parthian capital Ctesiphon.
• Continuing down the river, he took Charax on the Persian Gulf, his fleet surviving a Tidal Bore.
• Here he stopped, having left small garrisons of soldiers to control the occupied territory.
• Interestingly, he sent a letter to the Roman Senate apologising for not carrying on and invading India, as Alexander the Great had done.
• Trajan did not attempt to pursue the Parthian Army who had withdrawn beyond the Kushan Mountains into the Iranian Plateau.

The Roman Empire reaches its greatest extent (116 CE)

• In 116 CE coins were minted declaring Armenia and Mesopotamia were now Roman Provinces, along with a Province called Assyria.
• Osrhoene also became a Roman Client Kingdom.

Rebellions force Trajan to withdraw the Legions from Mesopotamia (115 CE)

• In 115 CE, a major Rebellion called the Kitos War, erupted, which forced Trajan to withdraw the Legions from Mesopotamia, and back to Syria.
• Uprisings started to occur, not only in the conquered territories, but also in Egypt, Judaea and Cyrenaica.
• The Legions were withdrawn from occupied Parthia, and dispersed to quell the various Rebellions.

The Death of Trajan (117 CE)

• Already unwell, Trajan fell seriously ill on the return journey to Rome whilst sailing past Turkey.
• He died in the port of Selinus, Turkey, and his body was brought back to Rome.

The Outcome

• Trajan’s successor Hadrian, adopted a Policy of Deterrence instead of War and the Roman dream of repeating Alexander the Great‘s domination of the East was over.
• In 121 CE, Hadrian negotiated a Peace Treaty with Parthia that prevented further conflict.
• Hadrian decided to avoid the huge expense of warfare, and not to conduct any wars during the next 21 years of his reign.
• Instead, Hadrian, adopted a policy of Deterrence, reinforcing every Frontier with well defended Walls or Limes. He insisted each Legion was constantly training for warfare.

Ctesiphon, Iraq