I hope this is being posted in the right part of the forum.
On Christmas Eve in 1914 there was a spontaneous halt to the guns on the western front during WW I. In the lull comes the voice of a German soldier singing Stille Nacht. The British troops recognized the melody as Silent Night and joined in. There was heard calls for visits across No Man's Land. Cigars, whiskey, jams, chocolate and other small gifts were exchange between the German and British troops. Soldiers from both sides gathered for funerals in No Man's Land as they read a passage from Psalm 23 (Psalm 22 in the DRB).
Again in 1915 “When the Christmas bells sounded in the villages of the Vosges behind the lines ..... something fantastically unmilitary occurred. German and French troops spontaneously made peace and ceased hostilities; they visited each other through disused trench tunnels, and exchanged wine, cognac and cigarettes for Westphalian black bread, biscuits and ham. This suited them so well that they remained good friends even after Christmas was over.”
Source - en.wikipedia.org
There was also a Christmas truce on Germany's eastern front in WW I between Russian and German troops.
There have been a few songs written about these Christmas truces. Here's five of them.
Christmas 1914 In no man's land
Christmas in the Trenches
Pipes Of Peace
And we can't forget Snoopy and the Red Baron
Every pope since John XXIII has encouraged Catholics to be conscientious objectors.