As it were breastplates of iron (w qwraka siderou). The qwrax was originally the breast (from the neck to the navel), then the breastplate, only N.T. usage ( Revelation 9:9Revelation 9:17 ; 1 Thessalonians 5:8 ; Ephesians 6:14 ). The armour for the breastplate was usually of iron (siderou, Revelation 2:27 ), but with the locusts it only seemed to be so (w). However, the scaly backs and flanks of the locusts do resemble coats of mail. "The locusts of the Abyss may be the memories of the past brought home at times of Divine visitation" (Swete). The sound of their wings (h pwnh twn pterugwn). Graphic picture of the onrush of the swarms of demonic locusts and the hopelessness of resisting them. As the sound of chariots, of many horses rushing to war (w pwnh armatwn ippwn pollwn trecontwn ei polemon). Both metaphors here, the clatter and clangour of the chariot wheels and the prancing of the horses are found in Joel 2:4 . Trecontwn is present active predicate participle of trecw, to run. Cf. 2 Kings 7:6 ; Jeremiah 47:3 .