Why doesn't God just dispatch the dragon? I mean if God is God and there is no other then the dragon is just another lizard and God could squash it like a bug, if you’ll pardon the mixed zoological metaphors. And if there is no room in heaven once the battle is won why not cast the dragon somewhere where no further harm can be done instead of just making him really, really angry and setting him loose on the earth? And by the way even a short time on a planet with a pissed off dragon is way too much time. But then this is Christian mythology and as such not meant to make sense in a literal fashion. The point of these few verses and indeed the whole book of Revelation is that the cosmic battle of the pre-creation past anticipated the cosmic battle on Calvary which insured that in the final future good triumphs over evil because love is stronger hate. That means in the present we do not live in fear of the Dragon but by faith in Jesus who did not cling to life even in the face of death on a cross.