The Korean War started in 1950 when tank-led North Korean troops invaded South Korea. The U.S. and 20 other allied countries fought on the side of South Korea under the U.N. flag.
Ban, who was attending a global forum on aid effectiveness in Busan, visited the U.N. Memorial Cemetery, the world's only U.N. cemetery that contains the remains of 2,300 foreign soldiers killed in the three-year war.
Ban, a former South Korean foreign minister, paid his respects to the fallen soldiers, saying, "Because of their sacrifices, the Republic of Korea enjoys much freedom today." The Republic of Korea is South Korea's official name.
"As a U.N. secretary-general and a Korean as well as a world citizen, I deeply appreciate them," Ban said, as he made the first visit to the cemetery by a U.N. chief.
Ban also expressed thanks for South Korea's dispatch of troops for U.N. peacekeeping missions.
"During the Korean War, Busan was a gateway for U.N. troops to Korea, but it is now a gateway to send troops to the world for U.N. peacekeeping operations," he said.