It does not have in view a military invasion. In fact, given that the demonic spirits perform signs in order to validate the words of “mouths,” we do well to think primarily of ideological unity among the kings and kingdoms of the world. They are united in their rejection of God the Almighty (and hence the Christ). Of course, that ideological, religious rejection of God does not exclude a militaristic expression of that rejection.
14 For they are demonic spirits, performing signs, who go abroad to the kings of the whole world, to assemble them for battle on the great day of God the Almighty.