And there are seven kings: five are fallen, and one is, and the other is not yet come; and when he cometh, he must continue a short space.
There are - or, 'they (the seven heads) are seven kings.' They are "mountains" (Revelation 17:9) in relation to the woman who sits on them; "kings" in relation to the beast of which they are heads.
Five ... one - `the five ... the one:' the first five are fallen (applicable not to forms of government, but to once powerful empires: Egypt (Ezekiel 29:1-21; Ezekiel 30:1-26), Assyria, Nineveh (Nahum 3:1-19), Babylon (Jeremiah 50:1-46; Jeremiah 51:1-64), Medo-Persia (Daniel 8:3-7; Daniel 8:20-22; Daniel 10:13; Daniel 11:2), Greece (Daniel 11:4). Rome was 'the one' existing in John's days. "Kings" stand for kingdoms, because these are represented in character by some one head, as Babylon by Nebuchadnezzar, Medo-Persia by Cyrus, Greece by Alexander, etc. But Elliott, The seventh short-lived ruling head, next after the sixth in John's time, with the Asiatic DIADEM (cf. Revelation 17:1), not the Roman laurel crown, is the new quadripartite headship, instituted by Diocletian, which was short-lived, falling after thirty years by Constantine's victory. The new head, out of the cicatrice of the old amputated seventh, is pagan, though professedly Christian, the eighth, yet one of the seven in character, the second beast, the papacy with its two lamb-horns, the secular and the regular clergy(?).
The other is not yet come. Not as Alford, the Christian empire beginning with Constantine; but the Germanic-Slavonic empire beginning and continuing beastlike, i:e., HEATHEN for only "a short space." The time when "it is not" (Revelation 17:11), is while it is "wounded to death" with the "deadly wound" (Revelation 13:3). The Christianization of the northern hordes which descended on Rome is the wound to the beast, answering to the earth swallowing up the flood (pagan tribes) sent by the dragon to drown the woman (Revelation 12:15-16). The emphasis is on "a short space" (first in the Greek); not on (as Alford) "he must continue." The external Christianization (while the beast's wound continues) has lasted more than fourteen centuries, since Constantine. Rome and the Greek churches partially healed the wound by restoring image-worship.