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.
North Korea
The Korean Demilitarized Zone with South Korea remains the most heavily fortified border in the world. Inter-Korean relations are at the core of North Korean diplomacy and have seen numerous shifts in the last few decades. North Korea's policy is to seek reunification without what it sees as outside interference, through a federal structure retaining each side's leadership and systems. In 1972, the two Koreas agreed in principle to achieve reunification through peaceful means and without foreign interference. On 10 October 1980 then North Korean president Kim Il-sung proposed a federation between North and South Korea named the Democratic Federal Republic of Korea in which the respective political systems would initially remain. However, relations remained cool well until the early 1990s, with a brief period in the early 1980s when North Korea offered to provide flood relief to its southern neighbor. Although the offer was initially welcomed, talks over how to deliver the relief goods broke down and none of the promised aid ever crossed the border.
The two countries also organized a reunion of 92 separated families.
The Sunshine Policy instituted by South Korean president Kim Dae-jung in 1998 was a watershed in inter-Korean relations. It encouraged other countries to engage with the North, which allowed Pyongyang to normalize relations with a number of European Union states and contributed to the establishment of joint North-South economic projects. The culmination of the Sunshine Policy was the 2000 Inter-Korean summit, when Kim Dae-jung visited Kim Jong-il in Pyongyang. Both North and South Korea signed the June 15th North–South Joint Declaration, in which both sides promised to seek peaceful reunification. On 4 October 2007, South Korean president Roh Moo-hyun and Kim Jong-il signed an eight-point peace agreement.
However, relations worsened in the late 2000s and early 2010s when South Korean president Lee Myung-bak adopted a more hard-line approach and suspended aid deliveries pending the de-nuclearization of the North. North Korea responded by ending all of its previous agreements with the South. It deployed additional ballistic missiles and placed its military on full combat alert after South Korea, Japan and the United States threatened to intercept a Unha-2 space launch vehicle. The next few years witnessed a string of hostilities, including the alleged North Korean involvement in the sinking of South Korean warship "Cheonan", mutual ending of diplomatic ties, a North Korean artillery attack on Yeonpyeong Island, and growing international concern over North Korea's nuclear program. In 2018, a détente developed at the Winter Olympics in the South.