In 42 BC, Parthian forces fought alongside the "Liberators" (the leaders of Caesar's assassination) against the Caesarians under Mark Antony and Octavian in the Battle of Philippi in the Liberators' civil war. After the Liberators' defeat, in an attempt to resurrect the Pompeian cause, general Quintus Labienus, who had been sent to Parthia to ask for assistance in the last civil war, joined the Parthians, and the Parthian king Orodes II sent him together with his son Pacorus I to invade eastern Roman territories[4] while Mark Antony was in Egypt with Cleopatra.[2]