Revelation 9:14

Loose the four angels; representing desolating powers which in the course of providence had been restrained, but were to be suffered for a time to scourge, desolate, and destroy a great portion of the earth. The number four may be here, as in chap Revelation 7:1, a symbol of universality.

In the great river Euphrates; a symbol of the region whence these four angels should come. The Turks or Othmans, to whom this woe-trumpet seems to refer, came from the vicinity of the Euphrates.