This post should have gone up earlier, but I only saw the 2005 movie Joyeux Noël last night. It's a fictionalized portrayal of real incidents that took place at Christmas during World War I in 1914 when numerous incidents of truces along the Western Front took place.
Here's a video someone posted several years ago with a song that tells the story:
music by Mike Harding
On YouTube, the following text (from Wikipedia) is posted beneath the video:
The truce began on Christmas Eve, December 24, 1914, when German troops began decorating the area around their trenches in the region of Ypres, Belgium, for Christmas. They began by placing candles on trees, then continued the celebration by singing Christmas carols, most notably Stille Nacht (Silent Night). The British troops in the trenches across from them responded by singing English carols.
The two sides continued by shouting Christmas greetings to each other. Soon thereafter, there were calls for visits across the "No Man's Land" where small gifts were exchanged — whisky, jam, cigars, chocolate, and the like. The artillery in the region fell silent that night. The truce also allowed a breathing spell where recently-fallen soldiers could be brought back behind their lines by burial parties. Proper burials took place as soldiers from both sides mourned the dead together and paid their respects. At one funeral in No Man's Land, soldiers from both sides gathered and read a passage from the 23rd Psalm: The Lord is my shepherd. I shall not want. He maketh me to lie down in green pastures. He leadeth me beside the still waters. He restoreth my soul. He leadeth me in the path of righteousness for his name's sake. Yea, though I walk through the valley of the shadow of death, I will fear no evil.
The truce spread to other areas of the lines, and there are many stories of football matches between the opposing forces. The film Joyeux Noël suggests that letters sent home from both British and German soldiers related that the score was 3-2 in favour of the Germans.
And here's a trailer from the movie (it's worth seeing even if Christmas is past):
Peace on Earth. It's not just for Christmas...