The following is Henry Alford’s commentary on Revelation 9:13-21, from The Greek Testament with a critically revised text, a digest of various readings, marginal references to verbal and idiomatic usage, prolegomena, and a critical and exegetical commentary, for the use of theological students and ministers. 3rd ed. by Henry Alford (1810-1871). Published 1856 by Rivingstons, Deighton, Bell, and Co. in London, Cambridge. pp. 644-648.
Link to source: http://archive.org/details/greektestamentwi5604alfo
The horses of the prophecy of the 2nd woe may allude to the horses mentioned in Zechariah 12, and 14.
In Zechariah’s prophecies, the armies of those who come against Jerusalem are not killed; instead, they are smitten with “astonishment,” and with “blindness,” and other plagues. This illustrates that they are involved in warfare of a spiritual nature, not a flesh and blood conflict.
The traditional interpretation of the second woe of Revelation 9 is that the horses in the prophecy are symbolic, and represent false teachers, and apostasy, which, it was believed, would become worse at the time of the end. The views of some of the early scholars of the church who studied the Apocalypse are considered in this post. Quotations and author information are adapted from Augustus Clissold, The spiritual exposition of the Apocalypse, Volume 2, 1851.
The following is a critique of a portion of an article published by Christian Courier, which discusses gehenna.
Neither the locust plague of the fifth trumpet, which is the first woe, nor the army of horses in the sixth trumpet, which is the 2nd woe, are able to bring the world to repentance. In the sixth trumpet, the horses represent people who lack spiritual understanding.
Several prophecies, including Joel 2, Rev. 9 & 19 speak of armies of horses, and horsemen. They are not literal horses, but figurative.
God’s promises to Abraham were connected with knowing God, as God’s revelations of himself were Abraham’s “exceeding great reward.”
“After these things the word of the Lord came unto Abram in a vision, saying, Fear not, Abram: I am thy shield, and thy exceeding great reward.” [Gen. 15:1]