When Narseh ascended the throne, the eastern portion of Mesopotamia (since 244) and all of Armenia (since 252) were under Iranian rule. The traditional notion of the western part of Armenia had been given to the Arsacid prince Tiridates III has been questioned. According to historian Ursula Weber, "It is quite certain" that the whole of Armenia continued to be a part of the Sasanian Empire in the 3rd century, until it was later ceded to the Romans in 298/9 after the Peace of Nisibis. The proposition of Narseh presumably following Shapur I's expansionistic approach does not match with his testimony in the Paikuli inscription; "And Caesar and the Romans were in gratitude (?) and peace and friendship with us." Contrary to the testimony, however, the two empires soon clashed with each other−in 296. From a Roman viewpoint, the mutual relations with Iran had been heavily strained due to the aggressive and expansionistic approach of Ardashir I and Shapur I. However, the conclusive causes for the Roman offensive was possibly due to their territorial losses and the disadvantageous change in the sphere of authority and influence in the Mesopotamian-Armenian lands in the 240s and 250s.