On Christmas day, December 25th, Santa will come to the good boys and girls, or, erm, battle commanders (although, because we're special, he may stick around longer). Santa is known to be a fool, thinking that he can spread cheer and merriness over the goddamn battlefield. This total disrespect of combat gets the military mad, so they set up a special mission for this day. It is the most handsomely paid special mission, even more than killing zombies.
The U.S. Military wants this guy eliminated, and is willing to pay handsomely those who manage to gib the fat dude and secure a cool ribbon. In addition, each commander who would rather be a bad-kid on the naughty-list will receive one free Ranger Training per deployment, along with respect and admiration.