Revelation 17:12; The Ten Horns are Ten Kings

Revelation 17:12  And the ten horns which thou sawest are ten kings, which have received no kingdom as yet; but receive power as kings one hour with the beast. 

Hence and from Rev 17:14, 16, it seems that these ten kings or kingdoms, are to be contemporaries with the beast in its last or eighth form, namely, Antichrist.

Revelation 17:14  These shall make war with the Lamb, and the Lamb shall overcome them: for he is Lord of lords, and King of kings: and they that are with him are called, and chosen, and faithful. 

Revelation 17:16  And the ten horns which thou sawest upon the beast, these shall hate the whore, and shall make her desolate and naked, and shall eat her flesh, and burn her with fire. 

Compare Daniel 2:34, 44, the stone smote the image upon his feet, that is, upon the ten toes, which are, in Daniel 2:41–44, interpreted to be “kings.”

Daniel 2:34  Thou sawest till that a stone was cut out without hands, which smote the image upon his feet that were of iron and clay, and brake them to pieces. 

Daniel 2:44  And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever. 

Daniel 2:41-44  And whereas thou sawest the feet and toes, part of potters’ clay, and part of iron, the kingdom shall be divided; but there shall be in it of the strength of the iron, forasmuch as thou sawest the iron mixed with miry clay. And asthe toes of the feet were part of iron, and part of clay, so the kingdom shall be partly strong, and partly broken. And whereas thou sawest iron mixed with miry clay, they shall mingle themselves with the seed of men: but they shall not cleave one to another, even as iron is not mixed with clay. And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever. 

The ten kingdoms are not, therefore, ten which arose in the overthrow of Rome (heathen), but are to rise out of the last state of the fourth kingdom under the eighth head. I agree with Alford that the phrase “as kings,” implies that they reserve their kingly rights in their alliance with the beast, wherein “they give their power and strength unto” him (Revelation 17:13).

Revelation 17:13  These have one mind, and shall give their power and strength unto the beast. 

They have the name of kings, but not with undivided kingly power [Wordsworth].

 Jamieson, R., Fausset, A. R., & Brown, D. (1997). Commentary Critical and Explanatory on the Whole Bible (Vol. 2, p. 592). Oak Harbor, WA: Logos Research Systems, Inc.