I can't let Armistice Day go by without playing this one at some point on radio.

Australian Light Horse in the Middle East were not allowed to bring their horses back to Oz (apart from one belonging to a general). In other countries, they gave the horses to farmers etc but it was reckoned the Arabs were pretty cruel to their mounts so they were to be put down.
Each man undertook to shoot his best friend's horse so no-one had to shoot their own!

http://www.youtube.com/watch?v=hniMrGeF4us&feature=related

It was not just people who made the supreme sacrifice.