"In fact, when the classic historicist position is studied, the fulfillment in the case of Islam and Revelation chapter nine is seen to be so striking and well attested that 'even advocates of other approaches who are adamant in their rejection of the historicist system of interpretation have admitted the convincing nature of this particular identification'" - Steve Gregg, commenting on Revelation 9:1-6 in Revelation: Four Views: A Parallel Commentary, p. 176). For much more on this topic see http://www.puritandownloads.com/islam-muslims-in-bible-prophecy-in-the-book-of-revelation/.
"It does seem that the fourth iron kingdom was in fact both the pre-Papal and the pre-Islamic undivided Pagan Roman Empire, as well as the later Western-Roman Papal and the contemporaneous Eastern-Roman Islamic Empire into which it then subdivided. Indeed, both 'Mahomet' and 'the Pope' -- as we have already seen -- Dr. Calvin called 'the two horns of Antichrist.' Thus they correspond to the two legs of the later Roman Empire - Islam and the Papacy." - Dr. Francis Nigel Lee, Calvin on Islam (2000), free online at http://www.dr-fnlee.org/calvin-on-islam/.