He first invaded the island of Kos, a very lucrative conquest (and probably the main reason for the invasion) as the Ptolemies of Egypt and many other nations and people (like the Jews of Alexandria) had stashed part of their treasury there.

Besides the treasuries Mithridates got a hold of young prince Ptolemy Auletes, who was being held safe on Kos.

[5] The Roman governor of Asia, Lucius Cassius, had fled to Rhodes and was marshalling the resistance against Mithridates on the island.

Demetrius' engineers had created a large mechanised siege tower called the Helepolis, but despite this taunting technology Rhodes came out with a win.

It was a large tower mounted on ships with bridges equipped to safely pass over city walls from sea.

A royal supply ship, secure in their belief the Rhodians were penned up in their harbour, ventured close to the port and was attacked and captured by a swift bireme.

Then, when the Pontic ships turned to break of their pointless pursuit, the Rhodians suddenly wheeled and hit their opponents from the rear.

Two Pontic ships were sunk, the rest scattered while the Rhodians sailed on and slipped back into their port almost unscathed.

The transports had arrived sooner than expected and in considerable disorder as a result of a storm which had swept them towards Rhodes.

Mithridates did not have his warfleet in position to properly protect his transports and now the Rhodians were among them burning, ramming and capturing ships.

Eventually, the Rhodians were persuaded to lend part of their navy to the Roman admiral Lucullus who was collecting a fleet for Rome.

[11] The war ended in a Roman victory which forced Mithridates to abandon all his conquests and return to Pontus.