The Roman–Parthian Wars (54 BC – 217 AD) were a series of conflicts between the Parthian Empire and the Roman Republic and Roman Empire.

Invasion of 195CE

In 195 CE, Septimius Severus led another Roman invasion of Mesopotamia. He occupied Seleucia and Babylon, however he was unable to take Hatra.
Later, he abandoned the invasion and came back to rome.

Invasion in 197CE

In early 197CE, Emperor Septimus Severus left Rome and again sailed to the east.
He embarked at Brundisium and probably landed at the port of Aegeae in Cilicia, travelling on to Syria by land.
In Syria, he gathered his army and crossed the Euphrates.
Abgar IX, King of Osroene was the ruler of Edessa, assisted Severus’ expedition by providing archers. King Khosrov I of Armenia also sent hostages, money and gifts.
Severus led his army to Nisibis, which his general Julius Laetus had prevented from falling into Parthian hands.
Afterwards Severus returned to Syria to plan a more ambitious campaign.

Invasion of 198CE

The next year he led another successful campaign against the Parthian Empire.
This time his legions sacked the Parthian royal city of Ctesiphon and he annexed the northern half of Mesopotamia to the empire.
For this achievement Severus took the title Parthicus Maximus, following the example of Trajan.

Legacy of Septimius Severus Parthian Campaign

These wars led to the Roman acquisition of northern Mesopotamia, as far as the areas around Nisibis and Singara
During his time in the east, though, Severus also expanded the Limes Arabicus, building new fortifications in the Arabian Desert from Basie to Dumatha.
Parthia empire collapsed and ultimately defeated by a Persian rebellion led by Ardashir I, who entered Ctesiphon in 226.
Under Ardashir and his successors, Persian-Roman conflict continued between the Sassanid Empire and Rome.