In modern society religion, ideology and nationalistic pride have become the primary sources of clashes between civilizations. But a hundred years ago religion was actually a source of unity.
Thus it was that on December 24th 1914, following the opening of World War I and Christian churches on both sides of enemy lines supporting the national stance of ethnic and/or religious superiority (basically saying 'God is on our side'), that the doomed soldiers who were sent to the front set aside their weapons and ignored orders.
Such an event hasn't happened again since then. The act of treason that occurred then would never happen today. Soldiers who did would be subject to summary execution (ie. shot on the spot for treason).
Thus it was that only 5 months into the conflict (and not knowing how long it would last) the first Christmas of World War I was not a slaughter-fest of artillery, machine gun and poison gas weaponry...
It was Christmas in the Trenches and the morale was low. Rats, disease, filth, the screams of wounded soldiers in the distance, the ominous presence of the enemy. It could have been a potential massacre. To boost morale the German Kaiser Wilhelm ordered 100,000 Christmas trees and millions of candles sent to the front.
It started with German troops on the opposite side of No Man's Land singing "Stille Nacht" (Silent Night). British, French, Scottish and Canadian troops joined in and in various spots along the 600 mile stretch of trenches the unusual event happened: The Christmas Truce of 1914.
It should be noted that MOST of the soldiers did not leave their posts. Instead they stood there dumbfounded, suspecting it was all a trick. But quite a few did leave their posts and surprisingly they were not given any serious punishment for it. (There were punishments later handed out, but none of them were severe.)
Those who did set down their weapons and wandered out on to No Man's Land which was quiet for the evening. They gathered up the corpses of the fallen, and what followed was a celebration of photographs from home, chocolate, cigarettes, beer, wine, schnapps and according to several reports, soccer games.
Fraternization with the enemy / treason is severely punishable, including the possibility of summary execution by a commanding officer. But there were too many troops that did it. An officer who shot his own men on Christmas Eve would have had a revolt on his hands.
A French film, “Joyeux Noel”, later tells the story of how this all happened and is adapted from the stories and letters from the soldiers who lived through the event. Letters from the actual event are actually quite valuable now. A remake of the film in 2005 makes it out to be to the Scottish who started it.
Now more religious people might say that the treasonous Christmas Eve of 1914 was the spirit of Christmas alive in the souls of those men... but religious historians are quick to point out Jesus was actually born in March and the festival of Christmas was moved to December 25th by the Roman Emperor Constantine to coincide with the Roman festival of Saturnalia. Prior to that gift giving was not part of Christmas, but a Saturnalia tradition.
Likewise Yule logs and Christmas trees are also pagan traditions. And Saint Nicholas (aka Santa Claus) was actually a 4th century Greek (270 - 343 AD) who would secretly give gifts to people all year round, usually in the form of coins. Saint Nicholas is the patron saint of sailors, merchants, archers, thieves, children and students.
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Thus one could argue it was the common humanity that the soldiers in the trenches felt on December 24th 1914. They were tired of war and were really only there because their country had asked them to...
But there is one story about Saint Nicholas which does pertain to war and death. Its depicted in the painting shown here, Saint Nicholas Saves Three Innocents from Death. Saint Nicholas preached the values of compassion for your fellow man and helping out those in need.
Thus humanity and compassion was probably what moved the troops in 1914. Sadly it was short lived.