There is a heavy strand of apocalyptic theology that sees this text (among others) as a reference to a final battle at the end of time, commonly at Armageddon (see also Revelation 16:14). As with so much in the book of Revelation, there is no need to understand these words in such literal fashion as to conclude that they describe a single war fought at a single place at a single time in history. The battle initially described in Genesis 3:15 is ongoing and flares up repeatedly, even at times in physical combat. Indeed, behind all wars in history is ultimately this spiritual duel between the seed of the woman and the seed of the serpent. As the dragon (that is, Satan) repeatedly attempted during the old dispensation to destroy the seed of the woman (see Revelation 12:4), so he throughout the new dispensation is furious with the woman and continually makes war on her offspring (Revelation 12:17).
19 And I saw the beast and the kings of the earth with their armies gathered to make war against him who was sitting on the horse and against his army.