Rivers dry out and refil all the time... especially snow fed exotic rivers like the Euphrates.
Rev 16:16. You should probably read the whole thing some time.
OK, I see what you're saying now. You can't claim that armageddon already happened just because there was a battle called "meggido". Do you not understand that there are prophecies that must be fulfilled before this even happens? You think that just because there was a battle called "meggido" means that the battle of armageddon already happened?
When in the past did the Euphrates river dry up, with eastern military forces using it as a location/pathway for military purposes?
In order for your argument to be valid, you need to prove:
1. The Euphrates river has dried up sometime in the past.
2. That after the Euphrates river dried up, eastern military forces began to use the river for military purposes.
Did both 1 and 2 happen in 1918 at your "battle of megiddo"? If not, then the "battle of megiddo" was not the fulfillment of Revelation 16:12.