Following the outbreak of the Third Mithridatic War, Mithridates VI of Pontus ("r". 119–63 BC), an ally of Tigranes II of Armenia, requested aid from Parthia against Rome, but Sinatruces refused help. When the Roman commander Lucullus marched against the Armenian capital Tigranocerta in 69 BC, Mithridates VI and Tigranes II requested the aid of Phraates III ("r". c. 71–58). Phraates did not send aid to either, and after the fall of Tigranocerta he reaffirmed with Lucullus the Euphrates as the boundary between Parthia and Rome.