But this could easily refer to the war in Heaven, not the union of Angel and Man.
You have the war in heaven--what caused the war?
And they are cast out of heaven--to where? It says he's cast out into the earth.
It says their crime is that they left their first estate--what does that mean? That's a willful disobedience--different from being thrown out--they left of their own free will.
Also, when does this war in heaven happen?
7And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels,
8And prevailed not; neither was their place found any more in heaven.
The war in rev 12 is about Jesus Christ. Before ths war in heaven took place Satan was free to go to and fro and in addition approach the throne of God. He did this on a regular basis in order to condemn the saints of their sins. Read the book of Job.
But after Jesus was born, we now have an advocate with the father so Satan is no longer allowed into heaven, hence the war takes place, michael casts him out and bans him from entering the heaven of God or the heaven of heavens.
17 And the seventy returned again with joy, saying, Lord, even the devils are subject unto us through thy name.
(A new power given to man)18 And he said unto them, I beheld Satan as lightning fall from heaven.
19 Behold, I give unto you power to tread on serpents and scorpions, and over all the power of the enemy: and nothing shall by any means hurt you. 20 Notwithstanding in this rejoice not, that the spirits are subject unto you; but rather rejoice, because your names are written in heaven.
Notice here that after the war takes place and Satan is cast upon the earth, these verses proclaim the following
9 And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him. 10 And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ
: for the accuser of our brethren is cast down, which accused them before our God day and night. 11 And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death.
So when did salvation and the kingdom of Christ come upon the earth? and when did we have the blood to overcome?
The time that Jesus Christ came to the earth.
So the war in heaven has nothing to do with the events of Genesis giants. Because Satan could freely enter Gods throne during Jobs time, which was a long time period after Genesis.
The tail that drew the third and cast them to the earth, could be the devil destroying a third of Gods angels, rather than recruiting them, for it does not sound like a recruitment, casting down to the earth, rather it sounds more like the devil smashed them down, but this last sentence is just something I thought of, but I belive the rest I said lines up perfectly with scripture.