Peace on earth goodwill toward men

Luke 2:8 Now there were in the same country shepherds living out in the fields, keeping watch over their flock by night. And an angel of the Lord stood before them, and the glory of the Lord shone around them, and they were greatly afraid. Then the angel said to them, “Do not be afraid, for behold, I bring you glad tidings (Gospel - Luke 4:18) of great joy which will be to all people. For there is born to you this day in the city of David a Savior, who is Christ the Lord. And this will be the sign to you: You will find a baby wrapped in swaddling clothes, lying in a manger.” And suddenly there was with the angel a multitude of heavenly angels praising God and saying: “Glory to God in the highest, And on earth peace, goodwill toward men!”

What was the sign?
A newborn baby safely wrapped and cradled, ready for life and growth (verse 52) - God in Heaven could now be seen on earth in human form.
Jesus would live a life of struggle and challenge against evil and adversity conquering on behalf of us who were to follow him, because He would die and rise again and send his Holy Spirit for his life to indwell us.

What would this mean for our lives?
We would know that God was with us and for us living his life through our lives of struggle and challenge against evil and adversity. That is being saved. (the ‘saved from what’ question). We are not saved from facing the struggles and the adversity but we are saved from having our souls being defeated and made hopeless..

What would this bring upon Earth?
Peace (oneness with God) on earth in the hearts of we who live in this reality, a peace that would flow from us into our world that surrounds us. And God would be glorified (be upon display).
The peace and oneness with God that we receive through his Spirit strengthens our hearts with hope and faith in a God that goes before us devising a way, his plan for us through all these things.

That plan is God’s strategy on our behalf, to carry and administer that peace and good will to others, to be the good news, the Gospel of peace in the world.

Isaiah 26:12 – Lord, You will establish peace for us, For You have also done all our works in us (done = ordained, contrived – devised a plan).