Now war arose in heaven: as the context makes clear, this is the dwelling place of God, not the sky. New Revised Standard Version uses more current English: “And war broke out in heaven.” Instead of war some translations have “a battle” (Bible en français courant, Biblia Dios Habla Hoy). The Greek noun translated war is related to the verb “to fight,” used twice in this same verse. In certain languages one must express this as “They began to fight one another in heaven.”

Michael and his angels: Michael is one of the archangels, who in Dan 10.21 is identified as the special protector of Israel (and see Jude 9). Michael’s angels are those under his command. They are God’s heavenly messengers and servants. Another way of expressing this is “One of God’s chief messengers (or, archangels), named Michael, along with other messengers under him, fought against (or, attacked) the dragon.”

It may be more natural to arrange the various items in this verse as follows: “Suddenly war broke out in heaven: the chief angel Michael and his angels attacked the dragon, and the dragon and his angels fought back.” If possible, the same word should be used for Michael’s angels and the dragon’s angels. In many languages where the term or expression for angels is, for example, “God’s messengers” or “heavenly messengers,” translators must find another expression for angels who serve the dragon. In such cases one may say, for example, “and the dragon and his supporters (or, messengers) fought back” or “… fought back against Michael.”

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .