By the time winter set in, the pattern of the next four years had been clearly established: a war of attrition involving trivial advances and retreats across a few acres of mud.
But as Christmas approached that year, something unexpected began unfolding. On the frontline sector south of Ypres, Belgium, German troops began decorating the area around their trenches for Christmas Eve. As Wikipedia describes it:
The Germans began by placing candles on their trenches and on Christmas trees, then continued the celebration by singing Christmas carols. The British responded by singing carols of their own. The two sides continued by shouting Christmas greetings to each other. Soon thereafter, there were excursions across No Man’s Land, where small gifts were exchanged, such as food, tobacco and alcohol, and souvenirs such as buttons and hats. The artillery in the region fell silent. The truce also allowed a breathing spell where recently killed soldiers could be brought back behind their lines by burial parties. Joint [religious] services were held.
The ceasefire spread to other sectors of the front, with as many as 100,000 men eventually participating. In some areas, soccer games between the belligerents replaced combat.
By December 26th, it was over. The authorities got word of the breakdown in discipline and intervened vigorously.
(The Occidental Observer, December 14, 2013).