“Thus, as peace began to be [established], the angels proclaimed, ‘Glory to God in the highest and peace on earth (Luke 2.14).’ When lower beings received [peace] from superior beings, they cried, ‘Glory on earth and peace in the heavens (Luke 19.38).’ At that time when the divinity came down and was clothed in humanity, the angels cried, ‘Peace on earth’. And at the time when that humanity ascended in order to be absorbed into the divinity and sit on the right –Peace in heaven, – the infants were crying forth before him, ‘Hosanna in the highest.’ Hence, the apostle also learned that one should say, ‘He made peace by the blood of his cross [for] that which is in heaven and on earth.” St. Ephrem the Syrian, Commentary on The Diatesseron, 2.14.
Christ, the peace of God, comes and establishes peace. He does this precisely because He is The Divine come and united to humanity. In this way, humanity which had previously lived in discord, is brought to wholeness once more. Humanity which was constantly wandering as nomads in the desert, swayed to and fro by sin (cf. the book of Judges and the constantly teetering of the people of Israel) is now brought to wholeness and peace by its union with God.
“He Who lives forever did not sink down into the conditions of a bodily birth from any need to live, but to call us back from death to life. Since, then, there was needed a lifting up from death for the whole of our nature, He stretches forth a hand as it were to prostrate man, and stooping down to our dead corpse He came so far within the grasp of death as to touch a state of deadness, and then in His own body to bestow on our nature the principle of the resurrection, raising as He did by His power along with Himself the whole man. For since from no other source than from the concrete lump of our nature had come that flesh, which was the receptacle of the Godhead and in the resurrection was raised up together with that Godhead.” St. Gregory of Nyssa, Catechetical Orations, 32.
By His very union with us, He saves us. Our problem is no abstract ‘flaw’, our problem is our separation from Life. Thus Life Himself comes and becomes one of us that He might make us whole. In this way, the warring factions of humanity are brought to accord by the Logos Who makes us whole. Death no longer holds sway over our life, through fear of which (cf. Heb 2.15) we were held in bondage to the passions. Now we are granted victory for we know the end to which we live, the Logos who came and became man.