“According to the Syrian writer Zenob, there was an Indian colony in the canton of Taron on the Upper Euphrates, to the west of Lake Van, as early as the second century B.C. The Indians built there two temples containing images of gods about 13 and 22 ft. high. When, about A.D. 304, St. Gregory came to destroy these temples, he was strongly opposed by the Indians. But he defeated them and smashed the images, thus anticipating the iconoclastic zeal of Mahmud of Ghazni.”
Note that, Zenob was an ancient Syrian historian/hagiographer ~300-400AD
Source: The History and Culture of the Indian People, Volume II: The Age of Imperial Unity, RC Mujumdar ( pages 633-634)
“St. Gregory appeared with 300 men to overturn their faith. The (Hindu) people flew to arms, and the first outbreak of the popular fury obliged St. Gregory to take refuge in a friendly castle. Both sides received reinforcements, desperate battles were fought, and over a thousand men fell. Artzan, the chief priest, and his son Demetr were slain in combat, having exhibited courage worthy of heroes. The Indians were overpowered, but they still implored that their idols might be spared. Six priests fell at the temple door, another died under torture without revealing the treasury of Demetr. The Christians then proceeded to break up the copper statues of the gods, which were 12 and 15 cubits high. The temples were razed to the ground, and on the site of Demetr's temple, St. Gregory erected a church, while a wooden cross marked the place where Gisanê's (Krishna) idol had stood. More than 5,000 idolaters submitted to baptism, and 438 persons, the sons of priests, or temple servants, who remained obdurate, had their heads shaved and were transported to Phaitakaran, near the shores of the Caspian”
Source: Kennedy, J. “ The Indians in Armenia (130 BC-300 AD)” from The Journal of the Royal Asiatic Society of Great Britain and Ireland (1904): 309-314.