A good example of why Men's Christmas Dinners have evolved in a particular way over time. The below account is of the famous Seaforth Highlanders of Canada Christmas dinner at Ortona in 1943. Many other regiments have held similar events down through the ages. Bottom line in the case of this particular military tradition ... miltary only.
The setting for the dinner was complete, long rows of tables with white tablecloths, and a bottle of beer per man, candies, cigarettes, nuts, oranges and apples and chocolate bars providing the extras. The C.O., Lt.-Col. S. W. Thomson, laid on that the Companies would eat in relays... as each company finished their dinner, they would go forward and relieve the next company... The menu... soup, pork with apple sauce, cauliflower, mixed vegetables, mashed potatoes, gravy, Christmas pudding and mince pie... From 1100 hours to 1900 hours, when the last man of the battalion reluctantly left the table to return to the grim realities of the day, there was an atmosphere of cheer and good fellowship in the church. A true Christmas spirit. The impossible had happened. No one had looked for a celebration this day. December 25th was to be another day of hardship, discomfort, fear and danger, another day of war. The expression on the faces of the dirty bearded men as they entered the building was a reward that those responsible are never likely to forget… During the dinner the Signal Officer... played the church organ and with the aid of the improvised choir, organized by the padre, carols rang out throughout the church."
- Seaforth Highlanders Regiment, War Diary, December 25th, 1943
http://www.junobeach.org/e/2/can-eve-rod-ita-ort-e.htm