Gyeongui Line (1904–1945)
Following Japan's defeat in the Pacific War and the subsequent partition of Korea, the Gyeongui Line was divided at the 38th parallel between North and South Korea. On 25 August 1945, the Soviet Army began operating trains on the line north of Sariwon, whilst trains in the south terminated at Gaeseong. In 1946, the railways in both North and South were nationalised, creating the Korean National Railroad in the South and the Korean State Railway in the North. After the Korean War, the Gyeongui Line was split into three sections. In the South, the Seoul–Jangdan section became the KNR's Gyeongui Line, retaining the same name; in the North, the Bongdong–Pyeongyang section became the P'yŏngbu Line, whilst the Pyeongyang–Sinuiju section became the P'yŏngŭi Line.
South Korea
Both North and South Korea claim complete sovereignty over the entire peninsula and outlying islands. Despite mutual animosity, reconciliation efforts have continued since the initial separation between North and South Korea. Political figures such as Kim Koo worked to reconcile the two governments even after the Korean War. With longstanding animosity following the Korean War from 1950 to 1953, North Korea and South Korea signed an agreement to pursue peace. On October 4, 2007, Roh Moo-Hyun and North Korean leader Kim Jong-il signed an eight-point agreement on issues of permanent peace, high-level talks, economic cooperation, renewal of train services, highway and air travel, and a joint Olympic cheering squad.
Despite the Sunshine Policy and efforts at reconciliation, the progress was complicated by North Korean missile tests in 1993, 1998, 2006, 2009, and 2013. , relationships between North and South Korea were very tense; North Korea had been reported to have deployed missiles, ended its former agreements with South Korea, and threatened South Korea and the United States not to interfere with a satellite launch it had planned. North and South Korea are still technically at war (having never signed a peace treaty after the Korean War) and share the world's most heavily fortified border. On May 27, 2009, North Korean media declared that the Armistice is no longer valid because of the South Korean government's pledge to "definitely join" the Proliferation Security Initiative. To further complicate and intensify strains between the two nations, the sinking of the South Korean warship Cheonan in March 2010, is affirmed by the South Korean government to have been caused by a North Korean torpedo, which the North denies. President Lee Myung-bak declared in May 2010 that Seoul would cut all trade with North Korea as part of measures primarily aimed at striking back at North Korea diplomatically and financially, except for the joint Kaesong Industrial Project, and humanitarian aid. North Korea initially threatened to sever all ties, to completely abrogate the previous pact of non-aggression, and to expel all South Koreans from a joint industrial zone in Kaesong, but backtracked on its threats and decided to continue its ties with South Korea. Despite the continuing ties, Kaesong industrial zone has seen a large decrease in investment and manpower as a result of this military conflict. In February 2016, the Kaesong complex was closed by Seoul in reaction to North Korea's launch of a rocket earlier in the month unanimously condemned by the United Nations security council.
The 2017 election of President Moon Jae-in has seen a change in approach towards the North, and both sides used the South Korean held 2018 Winter Olympics as an opportunity for engagement, with a very senior North Korean political delegation sent to the games, along with a reciprocal visit by senior South Korean cabinet members to the North soon afterwards.