Armenian History - Division of Armenia
During the first four centuries AD Armenia gradually lost its independence. Armenian kingdom was divided between two powerful empires – Roman Empire and Persian Sasanid state. Until the middle of the first century Armenian throne was taken by a variety of governors acceptable by Rome. Roman influence in Armenia started to concede to Oriental in the second half of the century. Armenian throne was taken by Trdat, the founder of new Arshakid dynasty. In response to that Roman emperor Neron sent his legions to the East.
Several years of war with Persians brought Romans no success and they were forced to make peace. Romans and Persians soon come to the agreement of dividing Armenian lands between them with the most part going to Persians. So in 428 Persian tsar Varakhran V turned Armenia into a province of Sasanid state and put an end to Arshakid dynasty.
But hundred years prior to that, in 301, Armenia had adopted Christianity as the state religion.