Matthew Henry Commentary Revelation 16:12-16

"And the sixth poured out his bowl upon the great river, the [river] Euphrates; and the water thereof was dried up, that the way might by made ready for the kings that [come] from the sunrising. And I saw [coming] out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet, three unclean spirits, as it were frogs: for they are spirits of demons, working signs; which go forth unto the kings of the whole world, to gather them together unto the war of the great day of God, the Almighty. (Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walked naked, and they see his shame.) And they gathered them together into the place which is called in Hebrew Har-magedon." — Revelation 16:12-16 (ASV)

This probably shows the destruction of the Turkish power and of idolatry, and that a way will be made for the return of the Jews. Alternatively, understand this as Rome, the mystical Babylon, with the name Babylon standing for Rome, which was intended but was not to be directly named at that time. When Rome is destroyed, her river and merchandise must suffer with her.

And perhaps a way will be opened for the eastern nations to come into the church of Christ. The great dragon will collect all his forces to make one desperate struggle before all is lost. God warns of this great trial to urge His people to prepare for it. These will be times of great temptation; therefore Christ, by His apostle, calls on His professed servants to expect His sudden coming and to watch that they might not be put to shame as apostates or hypocrites.

However Christians may differ in their views of the times and seasons of events yet to come to pass, on this one point all are agreed: Jesus Christ, the Lord of glory, will suddenly come again to judge the world. To those living near Christ, His coming is an object of joyful hope and expectation, and delay is not desired by them.