The character of the Male opera singer is based on that of German tenor Walter Kirchhoff (1879-1951), who travelled to the front in order to perform for the troops. His performance was met by cheers from the French lines, where upon he decided to climb on to no-mans-land to see who was cheering.
Towards the end of the film Major General Audebert says "i've been ordered to arrest a cat for treason", A cat portrayed in the film as Felix/Nestor, was actually arrested and shot for espionage after it arrived in French lines wearing a new collar and bearing a note (in french) which read "which regiment are you from?". The general in charge decided just to follow the letter of the law, the cat was shot for spying.
The football match depicted was probably inspired by the documented game between the 2nd Battalion The Royal Welsh Fusiliers and the Saxon Infantry who played football on Christmas Day 1914. In 2008 the British and German Armies sent teams France to play a game of football in honour of their predecessors.
As of October 2009, American composer Kevin Puts was writing a full-length opera based on this film for the Minnesota Opera. The opera, called Silent Night, was premiered in Minnesota in 2011, won the 2012 Pulitzer Prize for music, and was transferred to Opera Philadelphia in February 2013 with most of the same cast. Its libretto by Mark Campbell is extremely faithful to the movie's screenplay.
The Scottish regiment depicted in this film, judging by the badges displayed on the "Glengarry," were the Royal Scots Fusiliers. On December 20, 1914, the 2nd Argyle & Sutherland Highlanders took over the front line trenches at Houplines until after Christmas, it was widely reported at the time in numerous letters that it was this regiment that arranged to play a football match versus the Saxons in no man's land.