Image 0 of 5U.S. Air Force F-15C Strike Eagles taxi to the runway for takeoff Dec. 5, 2017, at Gwangju Air Base, Republic of Korea, during Exercise Vigilant Ace-18. (Airman 1st Class Kristen A. Heller/Air Force) Alaska National Guard crew members and volunteers prepare to board an HC-130J Combat King II, belonging to the 211th Rescue Squadron, after a successful Operation Santa Claus visit in St. Michael, Alaska, on Dec. 5, 2017. Operation Santa Claus is an Alaska National Guard annual community outreach program that provides Christmas gifts, books, backpacks filled with school supplies, fresh fruit and sundaes to children in rural communities. (2nd Lt. Marisa Lindsay/Army National Guard) A CH-53E Super Stallion helicopter picks up an AV-8B Harrier engine to during a Helicopter Support Team mission as part of Combined Composite Training Unit Exercise, Dec. 1, 2017, in the Atlantic Ocean. (Cpl. Jon Sosner/Marine Corps) A soldier assigned to 2nd Battalion, 70th Armor Regiment, 2nd Armored Brigade Combat Team, 1st Infantry Division from Fort Riley, Kan., scans the terrain over the sights of his M-249 machine gun Nov. 18, 2017, during an Allied Spirit VII training event in Grafenwoehr, Germany. (Spc. Dustin D. Biven/Army) Lt. Cmdr. Nate Michael, assigned to the "Gray Wolves" of Electronic Attack Squadron (VAQ) 142, returns to Naval Air Station Whidbey Islan, Wash., Dec. 4, 2017. The Gray Wolves completed a six-month deployment, operating in the U.S. 5th Fleet area of operations, with Carrier Air Wing (CVW) 11 while embarked aboard the Nimitz-class aircraft carrier USS Nimitz (CVN 77). (MC2 Joseph E. Montemarano/Navy)