Defense Secretary Jim Mattis greets Republic of Korea Air Force (ROKAF) Lt. Gen. Won, In-Choul, ROKAF Operations Command commander, as he arrives at Osan Air Base, 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.