Revelation 16:12
Upon the great river, the river Euphrates (epi ton potamon ton megan ton Eufrathn). The sixth trumpet brings up the river Euphrates also (Revelation 9:14), only there epi with the locative, while here epi with the accusative. Note triple use of the article ton here.
Was dried up (echranqh). First aorist (prophetic) passive of chrainw (Revelation 14:15). Cf. Zechariah 10:11.
That may be made ready (ina etoimasqh). Purpose clause with ina and the first aorist passive of etoimazw. Common verb in Rev. (Revelation 8:6; Revelation 9:7, Revelation 9:15; Revelation 12:6; Revelation 19:7; Revelation 21:2).
The way for the kings (h odov twn basilewn). Objective genitive basilewn.
That come from the sunrising (twn apo anatolhv eliou). "Those from the rising of the sun," the kings from the east (cf. Matthew 2:2) in their march against Rome. Parthia in particular resisted Rome before Trajan's day.
