Probably they had been all effected by the year B.C.

150; since there is reason to believe that about that time Mithridates found his power sufficiently established in the west to allow of his once more turning his attention eastward, and renewing his aggressions upon the Bactrian kingdom, which had passed from the rule of Eucratidas under that of his son and successor, Heliocles.
Heliocles, who was allowed by his father a quasi-royal position, obtained the full possession of the Bactrian throne by the crime of parricide.

It is conjectured that he regarded with disapproval his father's tame submission to Parthian ascendency, and desired the recovery of the provinces which Eucratidas had been content to cede for the sake of peace.

We are told that he justified his crime on the ground that his father was a public enemy; which is best explained by supposing that he considered him the friend of Bactria's great enemy, Parthia.
If this be the true account of the circumstances under which he became king, his accession would have been a species of challenge to the Parthian monarch, whose ally he had assassinated.

Mithridates accordingly marched against him with all speed, and, easily defeating his troops, took possession of the greater part of his dominion.