But I would be wrong. At least wrong in my initial understanding.
In Matthew 10:34 of the New Testament, Jesus said, "Think not that I am come to send peace on earth: I came not to send peace, but a sword."
Of course the conflict that Jesus spoke of wasn't over material gain but over one's very soul. The conflict would be people who make choices that benefit mankind against those who do not.
The key word here is choices. The Jesus's message wasn't about forcing everyone to think and behave as if they were automatons -- certainly not as robots all working together and easily achieving peace on earth. After all, if God is indeed almighty, he can simply control his subjects and make them follow his every direction. There would be no free will. It would not be very impressive. Instead, Jesus's message was about convincing and ultimately overcoming wills that choose not to go along with humanity.
As such, we will likely have more conflicts than fewer conflicts in the struggle against inhumanity.
Sun Tzu said, "For the enemy chariots captured, immediately change their banner and incorporate them into our own chariots. Likewise, enemy soldiers who come over to our side should be treated well. This is called defeating the enemy and becoming stronger."
The winning side that conquer the enemy intact, therefore, isn't simply stronger but also more compassionate. Why? Because one does not have true strength without also having the surplus and capability to be humane. It is a paradoxical and extraordinary option to have in war and conflict. And since this surplus and capability are rare in practice, we almost never see their paradoxical and extraordinary result.
Being and acting like a civilized, enlightened nation aren't easy and have never been easy throughout recorded history. Fortunately Sun Tzu's strategies allow for even numerically weak forces to be effectively strong if the leader is willing to put in the time and hard work to put them into practice.
Nevertheless a civilized, enlightened nation has its sword always ready, either to destroy the enemy or to subdue and make harmless the enemy. According to Sun Tzu, destroying the enemy should be the last resort, since the ideal goal is always to subdue the enemy. Any nation that is mighty can impose its will, but only a nation with also wisdom and thus compassion does not, even when it can. It thinks long term. This country decides to attract, inspire, and challenge people -- not only its citizens and allies but also its enemies. (Have there been cruel, reprehensible enemies of ours that are now among our closest allies?) So depending on who uses the sword, that sword can take away life or it can give life.
With sincere reading and understanding, how Jesus and Sun Tzu used their swords over 2000 years ago isn't difficult to speculate. What is difficult to speculate is how in the future their students would actually use theirs. Recorded history doesn't show an encouraging trend. This would depend on their sincere reading, understanding, and application.
So is Christmas really about peace on earth? No. Not yet. But it can be.