In 113, Trajan decided that the moment was ripe to resolve the "eastern question" once and for all time by the decisive defeat of Parthia and the annexation of Armenia; his conquests marked a deliberate change of Roman policy towards Parthia, and a shift of emphasis in the "grand strategy" of the empire.[5] In 114, Trajan invaded Armenia, annexed it as a Roman province, and killed Parthamasiris who was placed on the Armenian throne by his relative, the king of Parthia, Osroes I.[6] In 115, the Roman emperor overran northern Mesopotamia and annexed it to Rome as well; its conquest was deemed necessary, since otherwise the Armenian salient could be cut off by the Parthians from the south.[6] The Romans then captured the Parthian capital, Ctesiphon, before sailing downriver to the Persian Gulf.