North Korea and North Vietnam were Cold War socialist allies, sharing the mentality of divided nation. Pyongyang provided economic and military assistances to Hanoi during the Vietnam War because, in the view of North Korean leader Kim Il Sung, the prospect of Korean unification depended largely on the victory of North Vietnam over the United States. However, Pyongyang’s relations with Hanoi after 1975 deteriorated because of the latter’s tilt towards the Soviet Union and invasion of Cambodia, while the former adhered to the principle of non-alignment. Furthermore, Hanoi’s institution of Doi Moi reform in 1986 led to the establishment of diplomatic relations with South Korea in 1992. By the early 2010s, North Korea regained her interest in Vietnam as economic development model, albeit with some constraints.