Passage: The earliest enemies of the Parthians were the Seleucids in the west and the Scythians in the east. However, as Parthia expanded westward, they came into conflict with the Kingdom of Armenia, and eventually the late Roman Republic. Rome and Parthia competed with each other to establish the kings of Armenia as their subordinate clients. The Parthians soundly defeated Marcus Licinius Crassus at the Battle of Carrhae in 53 BC, and in 40–39 BC, Parthian forces captured the whole of the Levant except Tyre from the Romans. However, Mark Antony led a counterattack against Parthia, although his successes were generally achieved in his absence, under the leadership of his lieutenant Ventidius. Various Roman emperors or their appointed generals invaded Mesopotamia in the course of the ensuing Roman–Parthian Wars of the next few centuries. The Romans captured the cities of Seleucia and Ctesiphon on multiple occasions during these conflicts, but were never able to hold on to them. Frequent civil wars between Parthian contenders to the throne proved more dangerous to the Empire's stability than foreign invasion, and Parthian power evaporated when Ardashir I, ruler of Istakhr in Persis, revolted against the Arsacids and killed their last ruler, Artabanus IV, in 224 AD. Ardashir established the Sassanid Empire, which ruled Iran and much of the Near East until the Muslim conquests of the 7th century AD, although the Arsacid dynasty lived on through the Arsacid Dynasty of Armenia, the Arsacid dynasty of Iberia, and the Arsacid Dynasty of Caucasian Albania; all eponymous branches of the Parthian Arsacids.

Question: Who were the Parthians first enemies?
Seleucids