Power Of The Horses - Revelation 9:18-19

Revelation 9:18-19 ESV 

By these three plagues a third of mankind was killed, by the fire and smoke and sulfur coming out of their mouths. For the power of the horses is in their mouths and in their tails, for their tails are like serpents with heads, and by means of them they wound.

The image of these strange horses might be more understood in light of the passage from Isaiah shown below. The head of the horses may symbolize the leaders in that day who breathe the fire and smoke of Satan that reeks of sulfur, the scent of his kingdom.  

The serpents in the tail may symbolize the false prophets which continue speaking the lies of the great serpent Satan. 

Death is the business and work of these soldiers of rebellion. 

Isaiah 9:14-16

So the Lord cut off from Israel head and tail,

palm branch and reed in one day—

 the elder and honored man is the head,

and the prophet who teaches lies is the tail;

 for those who guide this people have been leading them astray,

and those who are guided by them are swallowed up.