Defense Secretary Jim Mattis greets ROK air force Lt. Gen. Won, In-Choul, ROKAF Operations Command commander, as he arrives at Osan Air Base, Republic of Korea, Feb. 2, 2017. Mattis’ visit to the ROK, the first such visit in his tenure as secretary of defense, comes in light of a year of strong provocations from North Korea, affirming the ironclad commitment the U.S. has in strengthening its robust alliance with the ROK. (U.S. Air Force photo by Staff Sgt. Jonathan Steffen)