What does Revelation 9:9 mean?
John's vision includes the spectacle of Satan releasing a horde of locust-like demons from the bottomless pit. Their purpose is to bring five months of excruciating pain, but not death, on nonbelievers. This passage fleshes out more details about their appearance, which includes a horse-like shape, human-like faces and hair, and lion-like teeth. The locusts' thoraxes resemble horses' armor plates, making them appear invulnerable. The noise of their flight, being so dense, resembles the loud sound of chariots and horses rushing into battle.Obviously, John's vision of future events leaves room for interpretation. Some passages in this writing seem extremely literal (Revelation 1:11), others clearly figurative (Revelation 7:1). Since this throng of locusts is demonic, interpreters differ on whether what John sees here is a literal vision, a metaphor, or possibly an attempt for an ancient writer to describe modern technology.
Some Bible teachers see this invasion of locusts as an end-times military invasion of infantry and heavily armed helicopters. The breastplates, they say, depict the armored fronts of the helicopters, and the loud noise is that of the numerous helicopters in flight. Obviously, the Bible predates modern warfare, and it would have been meaningless to believers in John's day and those of pre-modern times to use the term "helicopters." This could even, possibly, be a military technology that doesn't exist as of the time this commentary is being written. However, the description John provides fits the description of modern warfare, and so does Joel's description in Joel 2:5: "As with the rumbling of chariots, they leap on the tops of the mountains, like the crackling of a flame of fire devouring the stubble, like a powerful army drawn up for battle."
It is not beyond reason to perceive of the northern invader as rushing into Israel with helicopters and other military resources. The interpretation, of course, cannot be dogmatic. Prior verses seem to imply a narrow role for these "locusts" (Revelation 9:4–5), one not easily explained as a military operation.