Luke 10
17 And the seventy returned again with joy, saying, Lord, even the devils are subject unto us through thy name.
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.
What do you make of this passage?
Jesus does not say when He saw it. However, He never seems to discuss any specific experiences of His pre-incarnate existence, and there's no reason to think He's doing so here.
He may have seen it just that previous night. Or He may be speaking in prophesy.
We have to consider the uniqueness of Jesus. The concept is awesome. God becoming flesh--the concept of God Incarnate.
I don't think Satan had expected that--I don't think his understanding of the OT prophesies was any more accurate than that of the OT priests and scribes. I suspect Satan expected the Messiah to be a man on the order of David or Elijah. He may have thought Moses would be resurrected as the Messiah (there was something going on with the dispute he had with Michael over Moses' body).
I suspect Satan never expected that the Messiah would be God Incarnate.
And when he saw that happen, he must have wondered what it meant. He had successfully wrested control of the created dominion from Adam and all Adam's descendants. He had consigned them to physical death and separated their spirits from Heaven.
What exactly did God Incarnate mean in that situation? Did Satan now have power over God as he had over man? Was this some kind of capitulation? Satan's inquiring mind wanted to know.
So he had to test God Incarnate to find out. Upon testing, Satan discovered he had no power to subvert God Incarnate...but God Incarnate was yet physical, and being physical might be killed, and once killed would suffer the same separation from the Father as all other men before Him.
None of the rulers of this age understood it, for if they had, they would not have crucified the Lord of glory. -- 1 Corinthians 2:8
Somewhere in Satan's interaction with Jesus, he crossed a line he had not crossed before. He had actually
attacked God, which had not been possible before God became flesh.
I suspect the war in Heaven might have occurred while Jesus was in the grave. Notice that it's Michael leading the angels of heaven--where is Jesus? But when Satan is cast out, his war then is with those who are covered with the blood of the Lamb, so that is post-crucifixion.
How often was Satan cast out of heaven? It could only have been once, and as MiamiTed has pointed out, Revelation 12 bounds the war in heaven between the birth of Jesus and at some point when or soon after "the blood of the Lamb" has been shed.
At some point within that time, Jesus "led captivity captive" and brought the spirits that had been separated by the grave to be with Him--likely only possible because Satan was no longer there to argue their guilt, only the Son to argue for the Father's mercy. The prosecutor had been thrown out of the courtroom.