The KDX program was a three-phased program to modernize the surface fleet by developing and constructing new destroyers for the ROK Navy with advanced combat systems and weaponry. The outcomes of this program include the "Kwanggaeto the Great"-class destroyers, which are the first ROK destroyers to be armed with surface-to-air missiles; the "Chungmugong Yi Sunshin"-class destroyers; and the powerful , which are equipped with the sophisticated AEGIS combat system for air-defense and anti-missile operations. These new destroyers replaced antiquated destroyers that had been transferred from the U.S. Navy decades ago.