Julius Caesar sets out to avenge the defeat of Crassus against Parthia in 53 BCE where seven legions were lost. He sends one depleted legion from Syria to the mountainous regions of Armenia as a feint and two weeks later sets out in the direction of Ctesiphon with four legions, auxiliaries and 4000 cavalry from Gaul. A large engineering force is included for operating artillery and building defenses. The army is 40,000 strong overall. Ctesiphon is a Parthian capital city 500 km from the Syrian border. It is larger and richer than Rome itself. An ominous sign for the Parthians is the presence of legion X Equestris under the command of Publius Crassus.