"Peace I leave with you; My peace I give you; not as the world gives..." John 14:27
Peace is not the absence of conflict--that's called a truce. Peace is reconciliation between two estranged parties. Reconciliation means to become one or to become friends, which is very different from a truce.
In that light, man will never find lasting peace until he finds peace within himself, and we can't find peace within until we find peace with God. That peace is found through the person of Jesus Christ.
Christ did not come to bring peace on earth through peace treaties, but He came to reconcile sinful individuals with God. With that comes true inner peace. With inner peace comes the ability to live in peace with our fellow man.