16:12And the sixth angel poured out his bowl upon the great river, the Euphrates; and its water was dried up, that the way might be prepared for the kings from the east.
And the SIXTH ANGEL poured out his BOWL upon the great river, the EUPHRATES;
The Euphrates River is the eastern boundary of land given to Israel (Deuteronomy 1:7 and Deuteronomy 11:24). This boundary is important because Israel's judgments seem to be promulgated from this area. In the past, Jeremiah 13 was a judgment and this verse for the future.
Two thoughts exist as to what effect the fourth bowl (verses 8 and 9) will have on the Euphrates River.
and its water was dried up, that the WAY might be prepared for the KINGS from the EAST.
In the past, the Euphrates River literally has been a barrier to armies advancing from the east. To today's militaries, the river is little more than a nuisance.
The symbolic interpretation is that eastern religions will penetrate Judo Christian beliefs. That is quite plausible given the inroads that Islam has made around the world in the last several decades. It is hard, however, to imagine our Jewish friends accepting the Islamic faith (or any other eastern belief) but given how readily they turned to Baal in Old Testament times even though they were commanded not to worship those idols (Exodus 34:11-16), this, too, is possible.
One last thought: if water is the container of spirits (evil most likely - see Revelation 9:14), then there is no place for the invading evil spirits to rest (verses 13 and 14 and Luke 11:14-28). With the Euphrates River dried up, these evil forces will penetrate onward right to the valley where the mother of all wars will take place.