Under the last king, Mithradates Eupator, commonly called the Great, the realm of Pontus included not only Pontic Cappadocia but alsd the seaboard from the Bithynian frontier to Colchis, part of inland Paphlagonia, and Lesser Armenia (see under MrTHRADATES).
Nevertheless during the two Mithradatic wars they remained loyal to the republic, and in 88 successfully stood a siege by the Pontic king.
But the Christianization of the inland Pontic districts began only about the middle of the 3rd century and was largely due to the missionary zeal of Gregory Thaumaturgus, bishop of Neocaesarea.
At the beginning of the 5th century it seems to have been an entrepot of the Pontic grain trade, at a later date an Athenian monopoly (Herod.
The cause of rupture was the attack on Pontic territory by Nicomedes at the instigation of the Romans.
In the basin of the Rion, in that of the Chorokh (which runs off the Pontic highlands into the Black Sea south of Batum), and on the Black Sea littoral from Batum northwards to Sukhum-kaleh, and beyond, the climate is extremely hot and the rainfall heavy (see under Climate below).
Henceforward their military power declined and they fell at times under Pontic ascendancy, from which they were finally freed by the Mithradatic wars, in which they heartily supported Rome.
The chief incidents of Rhodian history during this period are a memorable siege by Demetrius Poliorcetes in 304, who sought in vain to force the city into active alliance with King Antigonus by means of his formidable fleet and artillery; a severe earthquake in 227, the damages of which all the other Hellenistic states contributed to repair, because they could not afford to see the island ruined; some vigorous campaigns against Byzantium, the Pergamene and the Pontic kings, who had threatened the Black Sea trade-route (220 sqq.), and against the pirates of Crete.