Spies of North Korea: The Theory and Practice of North Korean Espionage provides an analysis of North Korean communism, known as Juche ideology, as well as its ultimate foreign policy goal – the revolutionization of South Korea through the reunification of the two Koreas. This book is based on the research methodologies from both primary and secondary resources that are unique to this topic. Primary research was conducted through a series of interviews with a former senior-level North Korean intelligence officer, under the alias of Dr. Dong-sik Kim, one of the few NKIS officers who had completed the 10-year long North Korean spy-training program at Bureau 225 – the main component of the NKIS that conducts HUMINT and special operations as well as training its spies. Dr. Kim infiltrated South Korea and defected in 1995. Secondary research was based on analyses of several memoirs by former North Korean spies – written in both Korean and English – and specifically, copies of NKIS' indoctrination materials on Juche ideology, which were secretly transferred from Pyongyang to Seoul during Dr. Kim's infiltration operation into the South. Indeed, these resources were written by Hwang Jang Yeop, the architect of Juche ideology, and the highest ranking North Korean official who had ever defected to South Korea.