According to North Korean defector Ko Yŏng Hwan, North Korea completed construction of a long-range missile base at "Paeg'un-ri" 1986. Eya Osamu, a Japanese journalist, characterizes this base as a Nodong missile base. The base is located relatively close to the Chinese border, which could deter military strikes by South Korea or the United States against the base. Defector Im Yŏng Sŏn claims that North Korea launched the SA-2 surface-to-air missile (SAM) at the US SR-71 reconnaissance aircraft on 26 August 1981 from this site, which indicates the base's original or ongoing mission could include air defense. If Im's claims are true, it's odd that the SAM was fired from this site since it is relatively far from the Demilitarized Zone (DMZ) and the flight path of the SR-71 aircraft. There is a "Paeg'un-ri" (白雲里) in Chunghwa-kun (中和郡), which is in the southern part of Pyongyang, and an air defense unit could have been deployed here instead. It's possible that Im could have confused these two locations. [Note: "Paeg'un" is now a "dong," an administrative unit within the city of Kusŏng. It was probably changed from a "ri" to a "dong" in October 1967 when Kusŏng became a city.]

Sources:
[1] Interview with North Korean defector Im Yŏng Sŏn by Daniel A. Pinkston, senior research associate, Center for Nomproliferation Studies, 14 December 2001, Seoul;
[2] Testimony of Ko Yŏng Hwan, former North Korean Foreign Ministry official, before the US Senate, 21 October 1997; Han Kyŏng Hun, "Pukhan Missile Ŏdie Sumgyŏ Twŏnna/Chung Chŏpkyŏngjiyŏk Tŭng 10 Kos'e Palsakiji," Segye Ilbo, 7 August 1999, p. 5, in KINDS, www.kinds.or.kr;
[3] Federation of American Scientists, "North Korea Special Weapons Guide," www.fas.org.