King Tigranes II the Great of Armenia (r.c.95-c.55) and his ally Mithridates VI Eupator of Pontus had been humiliated by the Romans and his son and successor Artavasdes II understood to which state he would ally himself. Shortly after the beginning of his reign, he could prove his use to the new superpower, when the Roman general Crassus (one of the members of the First Triumvirate) decided to attack Parthia. Artavasdes promised auxiliaries.
Unfortunately, Crassus did not listen to Artavasdes' advice to advance through mountaineous Armenia, where he would be protected against Parthian cavalry attacks; instead, the Roman, having crossed the Euphrates, proceeded to Edessa, found himself under attack on the plain near Carrhae, and was defeated by the Parthian commander Surena in the marshes of the river Balikh (53 BCE).
At the same time, the Parthian king, Orodes II, attacked Armenia itself and forced Artavasdes to switch sides. So, he allied himself to Parthia; his sister married to Pacorus, the Parthian crown prince. This new alliance was very dangerous for the Roman Republic and the Roman governor of Cilicia, Cicero, was afraid of an invasion. It did not happen.
We hear of Artavasdes again after the Second Triumvirate had been formed. In 36 BCE, Mark Antony invaded Parthia, achieved some success, but lost many soldiers on his way back to the west. Artavasdes accepted many Roman soldiers but maintained his neutrality. Still, he was considered responsible for Antony's lack of success, and in 34 BCE, the Romans invaded Armenia. Artavasdes was taken captive, a son of Mark Antony and Cleopatra, Alexander Helios, was appointed as king of Armenia, and Artavasdes was executed after the battle of Actium (31 BCE).
Because Mark Antony and Cleopatra committed suicide in the same winter, Artavasdes was not succeeded by Alexander Helios but by Artaxias II.