BAGHDAD — Sgt. Martin Contreras dressed jollily but was ready to kill.
The 23-year-old soldier from San Diego spent Friday morning preparing for a mission to deliver the brigade’s deputy commander, Lt. Col. Darron Wright, to visit troops at two joint security stations west of the city.
Contreras pinned a stuffed reindeer just above his M9 pistol on his bulletproof vest and wore a Santa hat. But he and a younger soldier spent some pre-mission downtime discussing about when and how to fire during a mission.
“If Rudolph has to come off,” he said, patting the stuffed animal, “it’s going …