“But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law, to redeem them that were under the law, that we might receive the adoption of sons”.    Galatians 4:4-5
Christ was the One that at the appointed time was going to crush the head of the serpent. He was born of Mary, the virgin, in Bethlehem, as the prophet had said, and by the power of the Holy Spirit.
Christ was born to destroy the deeds and the kingdom of the Devil. We read in Rev. 12,
“And there appeared another wonder in heaven; and behold a great red dragon, having seven heads and ten horns, and seven crowns upon his heads. And his tail drew the third part of the stars of heaven, and did cast them to the earth: and the dragon stood before the woman which was ready to be delivered, for to devour her child as soon as it was born.
And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels, and prevailed not; neither was their place found any more in heaven.
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.
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.
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.”
The dragon, the old serpent, called the Devil and Satan was cast out by Christ and now the believers overcome him by the blood of the Lamb and by the Word of God.